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Lithium–sulfur batteries exhibit a high energy density of 2500–2600 Wh/kg with affordability and environmental advantages, positioning them as a promising next-generation energy source. However, the insulating nature of sulfur/Li2S and the rapid capacity fading due to the shuttle effect have hindered their commercialization. In this study, we propose a method to boost the performance of lithium–sulfur batteries by modifying the sulfur cathode with a coating layer composed of polyethyleneimine (PEI) and Super P conductive carbon. The PEI/Super P-modified electrode retained 73% of its discharge capacity after 300 cycles at the 2 C scan rate. The PEI/Super P coated layer effectively adsorbs lithium polysulfides, suppressing the shuttle effect and acting as an auxiliary electrode to facilitate the electrochemical reactions of sulfur/Li2S. We analyzed the PEI/Super P-modified electrodes using symmetric cells, electrochemical impedance spectroscopy, and cyclic voltammetry. The battery manufacturing method presented here is not only cost-effective but also industrially viable due to its compatibility with the roll-to-roll process. [ABSTRACT FROM AUTHOR]

This study investigates the formation characteristics of gas hydrate from bulk water as well as dispersed water in silica gel and dry water particles when they are exposed to natural gas. The inclusion process of methane, ethane, and propane molecules in hydrate cages were observed with in situ Raman spectroscopy, and the resulting cage occupancies were estimated from [sup.13]C NMR spectra. A high-pressure autoclave was used to monitor the formation process to determine hydrate onset time, initial growth rate, and conversion ratio. The obtained data from Raman spectra and gas consumption profiles suggested that hydrate formed within less than 20 min when the temperature is sufficiently lower than the hydrate equilibrium condition at a given pressure. Methane molecules started to occupy the small cages of structure II, but about 6 min later ethane and propane were also included in hydrate cages. [sup.13]C NMR spectroscopy confirms that only 23% of large cages of structure II are occupied by methane molecules when hydrate formed from dispersed water in silica gel, which was much less than 68% from dry water. These results suggest that the dispersion of water in silica gel and dry water would enhance the formation process by increasing gas-to-water ratio, although the composition of hydrate phase may vary depending on the formation condition. However the formation of hydrate in silica gel and dry water still provide an effective option to capture the natural gas without using complex rotating machineries. Key words: gas hydrates, formation kinetics, Raman spectroscopy, [sup.13]C NMR spectroscopy. La presente etude a pour but d'etudier les caracteristiques de formation d'hydrates de gaz dans l'eau liquide et a partir d'eau dispersee dans du gel de silice ou de particules seches contenant de l'eau lorsque ces corps sont exposes au gaz naturel. Nous avons observe le processus d'inclusion des molecules de methane, d'ethane et de propane dans les cages d'hydrates au moyen de la spectroscopie Raman in situ et nous avons estime les taux d'occupation des cages a partir des spectres RMN [sup.13]C. Nous avons suivi le processus de formation grace a un autoclave a haute pression afin de determiner le delai de formation des hydrates, la vitesse de croissance initiale et le taux de conversion. Les donnees obtenues a partir des spectres Raman et des profils de consommation de gaz laissent supposer que les hydrates se sont formes en moins de 20 minutes lorsque la temperature est suffisamment en de^a des conditions d'equilibre des hydrates a une pression donnee. Les molecules de methane ont d'abord occupe les petites cages de structure II, toutefois, environ 6 minutes plus tard, les molecules d'ethane et de propane etaient aussi incluses dans les cages d'hydrates. La spectroscopie RMN [sup.13]C confirme que seulement 23 % des grandes cages de structure II sont occupees par des molecules de methane lorsque les hydrates sont formes a partir d'eau dispersee dans du gel de silice, ce qui represente beaucoup moins que les 68 % qui sont occupees dans le cas des particules seches contenant de l'eau. Ces resultats laissent supposer que la dispersion de l'eau dans le gel de silice et dans les particules seches favoriserait le processus de formation grace a l'augmentation du rapport gaz-eau, quoique la composition de la phase d'hydrate puisse varier selon les conditions de formation. Il n'en demeure pas moins que la formation d'hydrates dans le gel de silice et dans les particules seches contenant de l'eau represente tout de meme une option efficace pour pieger le gaz naturel sans qu'une machinerie complexe a rotation soit necessaire. [Traduit par la Redaction] Mots-cles: hydrates de gaz, cinetique de formation, spectroscopie Raman, spectroscopie RMN [sup.13]C., Introduction Gas hydrates are nonstoichiometric crystalline compounds that are classified into three structural families, structure I, structure II, and structure H. (1) Light hydrocarbon molecules such as methane, ethane, and [...]

Ionic hydrates are known to form numerous clathrate structures in which either the cations or anions sit in cages and the counterions are incorporated into the water framework. Due to the inclusion of the ionic species, such ionic clathrate hydrates not only show many peculiar features such as metal ion encagement and superoxide ion generation, but also exhibit notable physicochemical properties such as outstanding ionic conductivity and thermal stability. Thus, the ionic clathrate hydrates are considered for their potential applicability in various fields, including those that involve solid electrolytes, gas sensors, and energy storage. In this study, we report the design, synthesis, and characterization of the first ionic clathrate hydrate of the hexagonal structure-H (Str.H) crystal type. Diethyl-dimethyl-ammonium hydroxide hydrate was synthesized with C[H.sub.4] and Xe as help gases, and the crystal structure was identified by powder X-ray diffraction analysis. Further confirmation of the formation of Str.H was obtained from Raman spectroscopy and [sup.13]C, [sup.129]Xe, and ²H solid-state NMR spectroscopy. From [sup.13]C NMR and ab initio calculations, it was shown that the quaternary ion occupies the large cage of Str.H with a conformation different from that in solution, due to constraints imposed by the dimensions of the cage. The H deficiency introduced by substitution of O[H.sup.-] for a water molecule appears, from [sup.129]Xe NMR, to be disordered over the framework, and, from ²H NMR, to substantially increase the rate of reorientational mobility of the D atoms in the framework, over that observed for a Str.I hydrate and for ice. The Str.H hydrates are commonly more stable than other structures, thus the present findings on the ionic Str.H clathrate hydrate may offer a new approach for improving the stability of ionic clathrate hydrates for their practical application. Key words: ionic clathrate hydrate, structure-H hydrate, quaternary ammonium salt, ionic conductivity. On sait que les hydrates ioniques forment de nombreuses structures en clathrate dans lesquelles les cations ou les anions sont encages et les contre-ions, incorpores dans la structure formee par les molecules d'eau. En plus de presenter de nombreuses caracteristiques particulieres comme l'encagement d'ions metalliques et lageneration d'ions superoxydes, ce type d'hydrates de gaz, en raison de l'inclusion des especes ioniques, dispose proprietes physicochimiques remarquables comme une conductivite ionique et une stabilite thermique exceptionnelle. Par consequent, les hydrates de gaz ioniques sont interessants du fait de leurs possibles applications dans divers domaines, notamment ceux des electrolytes solides, des capteurs de gaz et du stockage de l'energie. Dans le cadre de ces travaux, nous presentons la conception, la synthese et la caracterisation du premier hydrate de gaz ionique en clathrate de structure cristalline hexagonale de type H. Nous avons synthetise l'hydrate de l'hydroxyde de diethyldimethylammonium a l'aide du methane et du xenon comme gaz facilitants et caracterise la structure cristalline par diffraction des rayons X sur poudre. Une preuve additionnelle de la formation de la structure H a ete obtenue par analyses spectroscopiques Raman et RMN du [sup.13]C, du [sup.129]Xe et du ²H a l'etat solide. Nous avons montre, a partir des spectres RMN [sup.13]C et de calculs ab initio, que l'ion quaternaire occupe la grande cage de la structure H, dans une conformation qui differe de la conformation en solution a cause des contraintes imposees par les dimensions de la cage. Le deficit d'hydrogene cause par la substitution d'ions O[H.sup.-] par des molecules d'eau semble, selon l'analyse RMN [sup.129]Xe, etre distribue de facon desordonnee dans la structure et, selon l'analyse RMN ²H, causer une augmentation considerable du taux de mobilite reorientationnelle des atomes de deuterium dans la structure, et ce, par comparaison au taux observe pour la structure d'hydrate de type I dans la glace. Les hydrates de structure H sont habituellement plus stables que ceux d'autres structures : les presentes observations sur les hydrates de gaz ioniques en clathrate de structure H pourraient ouvrir la voie a une nouvelle approche permettant d'ameliorer la stabilite des hydrates de gaz ioniques en vue de leurs applications pratiques. [Traduit par la Redaction] Mots-cles: hydrate de gaz ionique en clathrate, hydrate de structure H, sel d'ammonium quaternaire, conductivite ionique., Introduction There is a broad range of inclusion compounds based on three dimensional hydrogen-bonded water frameworks forming cages stabilized by interactions with guest molecules that occupy the cages. Of these, [...]