Snapshot on Negative Electrode Materials for Potassium-Ion Batteries

Potassium-based batteries have recently emerged as a promising alternative to lithium-ion batteries. The very low potential of the K+/K redox couple together with the high mobility of K+ in electrolytes resulting from its weak Lewis acidity should provide high energy density systems operating with fast kinetics. However, potassium metal cannot be implemented in commercial batteries due to its high reactivity. As safety is one of the major concerns when developing new types of batteries, it is therefore crucial to look for materials alternative to potassium metal that electrochemically insert K+ at low potential. Here, the different types of negative electrode materials highlighted in many recent reports will be presented in detail. As a cornerstone of viable potassium-ion batteries, the choice of the electrolyte will be addressed as it directly impacts the cycling performance. Lastly, guidelines to a rational design of sustainable and efficient negative electrode materials will be proposed as open perspectives

Building First‑Year Medical Students’ Skills in Finding, Evaluating, and Visualizing Health Information Through a “Debunking Medical Myths” Curricular Module

To provide an online service learning opportunity for medical students during the COVID-19 pandemic, medical faculty and librarians developed and implemented a “Debunking Medical Myths” module in which students learned to search for emerging medical literature, evaluate evidence, and use that evidence to create an infographics debunking a COVID-19-related myth for a non-medical audience. The resultant infographics are visually appealing and designed to make complex health information easy to understand. The module was well-received by students, who demonstrated a nuanced understanding of the use of infographics to convey health information, and students’ work was evaluated highly by community members

Effects of Relaxation on Conversion Negative Electrode Materials for Li-Ion Batteries: A Study of TiSnSb Using 119Sn Mössbauer and 7Li MAS NMR Spectroscopies

Conversion materials were recently considered as plausible alternatives to conventional insertion negative electrode materials in lithium-ion batteries due to their large gravimetric and volumetric energy densities. The ternary alloy TiSnSb was recently proposed as a suitable negative electrode material due to its large capacity (550 mA h g–1) and rate capability over many cycles. TiSnSb has been investigated at the end of lithiation (discharge) using 119Sn Mössbauer and 7Li magic-angle spinning (MAS) NMR spectroscopies to determine the species formed, their relative stabilities and their behavior during relaxation. During discharge, TiSnSb undergoes a conversion reaction to produce a mixture of phases believed to consist of lithium antimonides, lithium stannides, and titanium metal. In situ 119Sn Mössbauer spectroscopy indicates the presence of Li7Sn2 at the end of discharge, while 7Li NMR experiments suggest the formation of two distinct Sn-containing species (tentatively assigned to Li7Sn2 and Li7Sn3), in addition to two Sb-containing species (tentatively assigned as Li3Sb and a non-stoichiometric phase of Li2Sb, Li2–xSb). To gain insight into the relative stabilities of the species formed, experiments have been completed under open circuit voltage conditions. A new Sn-based species has been identified via 119Sn Mössbauer spectroscopy at the end of relaxation. Similar changes are observed in the 7Li NMR spectra obtained during relaxation. The species created at the end of discharge are extremely unstable and spontaneously evolve towards delithiated phases. Surprisingly, it is possible to resume electrochemical cycling after relaxation. It is likely that this behavior can be extended to this family of electrode materials that undergo the conversion reaction

Pitch-based carbon/nano-silicon composite, an efficient anode for Li-ion batteries

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Prussian blue analogues for potassium-ion batteries: insights into the electrochemical mechanisms

A comprehensive description of the electrochemical mechanisms of the Prussian Blue Analogue (PBA) K1.67Mn0.65Fe0.35[Fe(CN)6]0.92\ub70.45H2O is obtained by combining several complementary ex situ and operando physico-chemical characterisation techniques. This particular PBA, which shows very good electrochemical performance as a cathode material in potassium-ion batteries (PIBs), undergoes three successive redox reactions during the (de-)potassiation that are hereby identified by ex situ57Fe M\uf6ssbauer spectroscopy and operando Mn and Fe K-edge X-ray absorption spectroscopy. These reactions come along with notable modifications of the crystal structure, which are followed in real time by operando X-ray diffraction. The correlation of these results, interpreted with the support of chemometric methods, also reveals the limitations of this PBA, probably related to the deactivation of the Mn undergoing extensive reversible Jahn-Teller distortion during cycling as well as possible dissolution in the electrolyte. These results underline that optimisation of the chemical composition of PBAs is a crucial step towards the preparation of reliable and stable PBA-based cathodes for PIBs

Dehydration of Alginic Acid Cryogel by TiCl4 vapor : Direct Access to Mesoporous TiO2@C Nanocomposites and Their Performance in Lithium-Ion Batteries

A new strategy for the synthesis of mesoporous TiO2@C nanocomposites through the direct mineralization of seaweed-derived alginic acid cryogel by TiCl4 through a solid/vapor reaction pathway is presented. In this synthesis, alginic acid cryogel can have multiple roles; i) mesoporous template, ii) carbon source, and iii) oxygen source for the TiO2 precursor, TiCl4. The resulting TiO2@alginic acid composite was transformed either into pure mesoporous TiO2 by calcination or into mesoporous TiO2@C nanocomposites by pyrolysis. By comparing with a nonporous TiO2@C composite, the importance of the mesopores on the performance of electrodes for lithium-ion batteries based on mesoporous TiO2@C composite was clearly evidenced. In addition, the carbon matrix in the mesoporous TiO2@C nanocomposite also showed electrochemical activity versus lithium ions, providing twice the capacity of pure mesoporous TiO2 or alginic acid-derived mesoporous carbon (A600). Given the simplicity and environmental friendliness of the process, the mesoporous TiO2@C nanocomposite could satisfy the main prerequisites of green and sustainable chemistry while showing improved electrochemical performance as a negative electrode for lithium-ion batteries

Double-walled carbon nanotubes, a performing additive to enhance capacity retention of antimony anode in potassium-ion batteries

The effect of carbon additives on electrode formulation of bulk antimony was investigated in potassium-ion batteries. Several types of carbon including conventional carbon black, graphite and double-walled carbon nanotubes (DWCNT), employed as conductive agents, were found to play a non-negligible role on the electrochemical performance of antimony. While DWCNT alone show no reversible K+ storage compared to the other carbons, the Sb/DWCNT electrode exhibits better capacity retention and rate capability than Sb formulated with usual carbon additives or even with graphite. This can be ascribed to the specific structure of DWCNT acting not only as conductive additive but also as a mechanical reinforcement for the whole electrode, which has to withstand the large volume change of antimony during potassiation/depotassiation cycles

Atomic layer fluorination of 5 V class positive electrode material LiCoPO4 for enhanced electrochemical performance

EJK would like to thank the Alistore ERI for the award of a studentship. The authors thank EPSRC Capital for Great Technologies Grant EP/L017008/1. The authors want to thank the French Research Network on the Electrochemical Energy Storage (RS2E) for YCB’s PhD grant. MD and NL are indebted to the IR-RMN-THC FR3050 CNRS for the spectrometer time access and the financial support of the NMR experiments.The surface fluorination of lithium cobalt phosphate (LiCoPO4, LCP) using a one‐step, room temperature processable, easily up‐scalable and dry surface modification method with XeF2 as fluorine source was developed. After fluorination, fluorine‐rich nanoparticles were observed mainly on the particle surface, which facilitates the improvement of surface stability and electrochemical performance such as cycling stability and rate capability, as the fluorinated LCP can be protected against side reactions with electrolyte or by‐products of electrolyte decomposition at high voltage (5 V). More importantly, the direct surface fluorination proved more efficient than adding a fluorinated electrolyte additive (i. e., FEC). These results suggest that surface fluorination using XeF2 is of great promise for practical applications of high voltage positive materials for lithium‐ion batteries.PostprintPeer reviewe

Medullary control of nociceptive transmission: reciprocal dual communication with the spinal cord

Control of pain perception, essential for organism surviving and recovery from disease, is exerted by higher brain centers integrating nociception with emotional and cognitive information and modulating the brainstem-spinal feedback loops that regulate spinal nociceptive transmission. Development of chronic pain deregulates the forebrain-brainstem-spinal pain control system, which leads to neuroplasticity and disruption of a balanced brain-spinal communication. Targets for impeding pain chronification are being developed using the manipulation of the cross talk between brain and dorsal horn, at both sites of the loop.FCT -Fuel Cell Technologies Program(POCTI/NSE/46399/2002