scholarly journals Understanding Sulfur Redox Mechanisms in Different Electrolytes for Room-Temperature Na–S Batteries

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Hanwen Liu ◽  
Wei-Hong Lai ◽  
Qiuran Yang ◽  
Yaojie Lei ◽  
Can Wu ◽  
...  
Keyword(s):  
Room Temperature ◽  
High Surface ◽  
Reversible Capacity ◽  
High Loading ◽  
Side Reactions ◽  
Liquid Sulfur ◽  
Shuttle Effect ◽  
Loading Ratio ◽  
Solid Liquid ◽  
Sulfur Cathodes

Abstract This work reports influence of two different electrolytes, carbonate ester and ether electrolytes, on the sulfur redox reactions in room-temperature Na–S batteries. Two sulfur cathodes with different S loading ratio and status are investigated. A sulfur-rich composite with most sulfur dispersed on the surface of a carbon host can realize a high loading ratio (72% S). In contrast, a confined sulfur sample can encapsulate S into the pores of the carbon host with a low loading ratio (44% S). In carbonate ester electrolyte, only the sulfur trapped in porous structures is active via ‘solid–solid’ behavior during cycling. The S cathode with high surface sulfur shows poor reversible capacity because of the severe side reactions between the surface polysulfides and the carbonate ester solvents. To improve the capacity of the sulfur-rich cathode, ether electrolyte with NaNO3 additive is explored to realize a ‘solid–liquid’ sulfur redox process and confine the shuttle effect of the dissolved polysulfides. As a result, the sulfur-rich cathode achieved high reversible capacity (483 mAh g−1), corresponding to a specific energy of 362 Wh kg−1 after 200 cycles, shedding light on the use of ether electrolyte for high-loading sulfur cathode.

scholarly journals Supercooled liquid sulfur maintained in three-dimensional current collector for high-performance Li-S batteries

2020 ◽  
Vol 6 (21) ◽  
pp. eaay5098 ◽  
Author(s):  
Guangmin Zhou ◽  
Ankun Yang ◽  
Guoping Gao ◽  
Xiaoyun Yu ◽  
Jinwei Xu ◽  
...  
Keyword(s):  
High Performance ◽  
Critical Role ◽  
Three Dimensional ◽  
Current Collector ◽  
Reversible Capacity ◽  
Supercooled Liquid ◽  
High Energy ◽  
Liquid Sulfur ◽  
Sulfur Species ◽  
Solid Liquid

In lithium-sulfur (Li-S) chemistry, the electrically/ionically insulating nature of sulfur and Li2S leads to sluggish electron/ion transfer kinetics for sulfur species conversion. Sulfur and Li2S are recognized as solid at room temperature, and solid-liquid phase transitions are the limiting steps in Li-S batteries. Here, we visualize the distinct sulfur growth behaviors on Al, carbon, Ni current collectors and demonstrate that (i) liquid sulfur generated on Ni provides higher reversible capacity, faster kinetics, and better cycling life compared to solid sulfur; and (ii) Ni facilitates the phase transition (e.g., Li2S decomposition). Accordingly, light-weight, 3D Ni-based current collector is designed to control the deposition and catalytic conversion of sulfur species toward high-performance Li-S batteries. This work provides insights on the critical role of the current collector in determining the physical state of sulfur and elucidates the correlation between sulfur state and battery performance, which will advance electrode designs in high-energy Li-S batteries.

A Study on the Rearrangement of Dialkyl 1-Aryl-1-hydroxymethylphosphonates to Benzyl Phosphates

2020 ◽  
Vol 24 (4) ◽  
pp. 465-471 ◽  
Author(s):  
Zita Rádai ◽  
Réka Szabó ◽  
Áron Szigetvári ◽  
Nóra Zsuzsa Kiss ◽  
Zoltán Mucsi ◽  
...  
Keyword(s):  
Quantum Chemical ◽  
Room Temperature ◽  
Phase Transfer ◽  
One Pot ◽  
Substrate Dependence ◽  
Triethylbenzylammonium Chloride ◽  
One Step ◽  
The Pudovik Reaction ◽  
The One ◽  
Solid Liquid

The phospha-Brook rearrangement of dialkyl 1-aryl-1-hydroxymethylphosphonates (HPs) to the corresponding benzyl phosphates (BPs) has been elaborated under solid-liquid phase transfer catalytic conditions. The best procedure involved the use of triethylbenzylammonium chloride as the catalyst and Cs2CO3 as the base in acetonitrile as the solvent at room temperature. The substrate dependence of the rearrangement has been studied, and the mechanism of the transformation under discussion was explored by quantum chemical calculations. The key intermediate is an oxaphosphirane. The one-pot version starting with the Pudovik reaction has also been developed. The conditions of this tandem transformation were the same, as those for the one-step HP→BP conversion.

A Facile, Efficient and Selective Deprotection of P - Methoxy Benzyl Ethers Using Zinc (II) Trifluoromethanesulfonate

2019 ◽  
Vol 16 (12) ◽  
pp. 955-958
Author(s):  
Reddymasu Sireesha ◽  
Reddymasu Sreenivasulu ◽  
Choragudi Chandrasekhar ◽  
Mannam Subba Rao
Keyword(s):  
Room Temperature ◽  
Protecting Groups ◽  
Side Reactions ◽  
Reaction Conditions ◽  
Acid Sensitivity ◽  
Time Period ◽  
Protective Groups ◽  
Benzyl Ethers ◽  
Last Stage ◽  
Zinc Triflate

: Deprotection is significant and conducted over mild reaction conditions, in order to restrict any more side reactions with sensitive functional groups as well as racemization or epimerization of stereo center because the protective groups are often cleaved at last stage in the synthesis. P - Methoxy benzyl (PMB) ether appears unique due to its easy introduction and removal than the other benzyl ether protecting groups. A facile, efficient and highly selective cleavage of P - methoxy benzyl ethers was reported by using 20 mole% Zinc (II) Trifluoromethanesulfonate at room temperature in acetonitrile solvent over 15-120 min. time period. To study the generality of this methodology, several PMB ethers were prepared from a variety of substrates having different protecting groups and subjected to deprotection of PMB ethers using Zn(OTf)2 in acetonitrile. In this methodology, zinc triflate cleaves only PMB ethers without affecting acid sensitivity, base sensitivity and also chiral epoxide groups.

scholarly journals Lithium-mediated Ferration of Fluoroarenes

2020 ◽  
Vol 74 (11) ◽  
pp. 866-870
Author(s):  
Lewis C. H. Maddock ◽  
Alan Kennedy ◽  
Eva Hevia
Keyword(s):  
Hydrogen Atom ◽  
Organometallic Chemistry ◽  
Room Temperature ◽  
Structural Elucidation ◽  
Side Reactions ◽  
Metal Base ◽  
Lithium Amide ◽  
Mixed Metal ◽  
Important Challenge

While fluoroaryl fragments are ubiquitous in many pharmaceuticals, the deprotonation of fluoroarenes using organolithium bases constitutes an important challenge in polar organometallic chemistry. This has been widely attributed to the low stability of the in situ generated aryl lithium intermediates that even at –78 °C can undergo unwanted side reactions. Herein, pairing lithium amide LiHMDS (HMDS = N{SiMe3}2) with FeII(HMDS)2 enables the selective deprotonation at room temperature of pentafluorobenzene and 1,3,5-trifluorobenzene via the mixed-metal base [(dioxane)LiFe(HMDS)3] (1) (dioxane = 1,4-dioxane). Structural elucidation of the organometallic intermediates [(dioxane)Li(HMDS)2Fe(ArF)] (ArF = C6F5, 2; 1,3,5-F3-C6H2, 3) prior electrophilic interception demonstrates that these deprotonations are actually ferrations, with Fe occupying the position previously filled by a hydrogen atom. Notwithstanding, the presence of lithium is essential for the reactions to take place as Fe II (HMDS)2 on its own is completely inert towards the metallation of these substrates. Interestingly 2 and 3 are thermally stable and they do not undergo benzyne formation via LiF elimination.

scholarly journals Hierarchical Porous, N-Containing Carbon Supports for High Loading Sulfur Cathodes

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 408
Author(s):  
Jae-Woo Park ◽  
Hyun Jin Hwang ◽  
Hui-Ju Kang ◽  
Gazi A. K. M. Rafiqul Bari ◽  
Tae-Gyu Lee ◽  
...  
Keyword(s):  
High Energy ◽  
High Energy Density ◽  
High Loading ◽  
Carbon Supports ◽  
Structure Directing Agent ◽  
Shuttle Effect ◽  
Main Challenge ◽  
Hierarchical Porous ◽  
Hollow Carbon ◽  
A Minor

The lithium-polysulfide (LiPS) dissolution from the cathode to the organic electrolyte is the main challenge for high-energy-density lithium-sulfur batteries (LSBs). Herein, we present a multi-functional porous carbon, melamine cyanurate (MCA)-glucose-derived carbon (MGC), with superior porosity, electrical conductivity, and polysulfide affinity as an efficient sulfur support to mitigate the shuttle effect. MGC is prepared via a reactive templating approach, wherein the organic MCA crystals are utilized as the pore-/micro-structure-directing agent and nitrogen source. The homogeneous coating of spherical MCA crystal particles with glucose followed by carbonization at 600 °C leads to the formation of hierarchical porous hollow carbon spheres with abundant pyridinic N-functional groups without losing their microstructural ordering. Moreover, MGC enables facile penetration and intensive anchoring of LiPS, especially under high loading sulfur conditions. Consequently, the MGC cathode exhibited a high areal capacity of 5.79 mAh cm−2 at 1 mA cm−2 and high loading sulfur of 6.0 mg cm−2 with a minor capacity decay rate of 0.18% per cycle for 100 cycles.

scholarly journals Porous Carbon Architecture Assembled by Cross-Linked Carbon Leaves with Implanted Atomic Cobalt for High-Performance Li–S Batteries

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Ruirui Wang ◽  
Renbing Wu ◽  
Chaofan Ding ◽  
Ziliang Chen ◽  
Hongbin Xu ◽  
...  
Keyword(s):  
Active Sites ◽  
High Performance ◽  
Specific Capacity ◽  
Three Dimension ◽  
Zeolitic Imidazolate Framework ◽  
Shuttle Effect ◽  
Promising Solution ◽  
Fading Rate ◽  
Kinetics Of ◽  
Sulfur Cathodes

AbstractThe practical application of lithium–sulfur batteries is severely hampered by the poor conductivity, polysulfide shuttle effect and sluggish reaction kinetics of sulfur cathodes. Herein, a hierarchically porous three-dimension (3D) carbon architecture assembled by cross-linked carbon leaves with implanted atomic Co–N4 has been delicately developed as an advanced sulfur host through a SiO2-mediated zeolitic imidazolate framework-L (ZIF-L) strategy. The unique 3D architectures not only provide a highly conductive network for fast electron transfer and buffer the volume change upon lithiation–delithiation process but also endow rich interface with full exposure of Co–N4 active sites to boost the lithium polysulfides adsorption and conversion. Owing to the accelerated kinetics and suppressed shuttle effect, the as-prepared sulfur cathode exhibits a superior electrochemical performance with a high reversible specific capacity of 695 mAh g−1 at 5 C and a low capacity fading rate of 0.053% per cycle over 500 cycles at 1 C. This work may provide a promising solution for the design of an advanced sulfur-based cathode toward high-performance Li–S batteries.

scholarly journals Three-dimensional platinum nanoparticle-based bridges for ammonia gas sensing

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Nishchay A. Isaac ◽  
Johannes Reiprich ◽  
Leslie Schlag ◽  
Pedro H. O. Moreira ◽  
Mostafa Baloochi ◽  
...  
Keyword(s):  
Room Temperature ◽  
Gas Sensing ◽  
Response Times ◽  
High Surface ◽  
Three Dimensional ◽  
Performance Testing ◽  
Volume Ratio ◽  
Platinum Nanoparticle ◽  
Ammonia Gas ◽  
Lift Off

AbstractThis study demonstrates the fabrication of self-aligning three-dimensional (3D) platinum bridges for ammonia gas sensing using gas-phase electrodeposition. This deposition scheme can guide charged nanoparticles to predetermined locations on a surface with sub-micrometer resolution. A shutter-free deposition is possible, preventing the use of additional steps for lift-off and improving material yield. This method uses a spark discharge-based platinum nanoparticle source in combination with sequentially biased surface electrodes and charged photoresist patterns on a glass substrate. In this way, the parallel growth of multiple sensing nodes, in this case 3D self-aligning nanoparticle-based bridges, is accomplished. An array containing 360 locally grown bridges made out of 5 nm platinum nanoparticles is fabricated. The high surface-to-volume ratio of the 3D bridge morphology enables fast response and room temperature operated sensing capabilities. The bridges are preconditioned for ~ 24 h in nitrogen gas before being used for performance testing, ensuring drift-free sensor performance. In this study, platinum bridges are demonstrated to detect ammonia (NH3) with concentrations between 1400 and 100 ppm. The sensing mechanism, response times, cross-sensitivity, selectivity, and sensor stability are discussed. The device showed a sensor response of ~ 4% at 100 ppm NH3 with a 70% response time of 8 min at room temperature.

Fast Polysulfides Catalytic Conversion and Self-Repairing Ability for High Loading Lithium-Sulfur Batteries using a Permselective Coating Layer Modified Separator

Nanoscale ◽  
2021 ◽  
Author(s):  
Fanglei Zeng ◽  
Fang Wang ◽  
Ning Li ◽  
Ke Meng Song ◽  
Shi-Ye Chang ◽  
...  
Keyword(s):  
Energy Density ◽  
Coating Layer ◽  
High Energy ◽  
High Energy Density ◽  
High Loading ◽  
Battery System ◽  
Shuttle Effect ◽  
Lithium Sulfur Batteries ◽  
Lithium Sulfur ◽  
Modified Separator

Li-S battery is considered as one of the most promising battery system because of its large theoretical capacity and high energy density. However, the “shuttle effect” of soluble polysulfides and...

scholarly journals Facile Fabrication of Multifunctional ZnO Urchins on Surfaces

2018 ◽  
Vol 2 (4) ◽  
pp. 74 ◽  
Author(s):  
Abinash Tripathy ◽  
Patryk Wąsik ◽  
Syama Sreedharan ◽  
Dipankar Nandi ◽  
Oier Bikondoa ◽  
...  
Keyword(s):  
Contact Angle ◽  
Water Contact Angle ◽  
Surface Density ◽  
Room Temperature ◽  
High Surface ◽  
Secondary Growth ◽  
Water Contact ◽  
Growth Step ◽  
Si Substrates ◽  
Wide Range

Functional ZnO nanostructured surfaces are important in a wide range of applications. Here we report the simple fabrication of ZnO surface structures at near room temperature with morphology resembling that of sea urchins, with densely packed, μm-long, tapered nanoneedles radiating from the urchin center. The ZnO urchin structures were successfully formed on several different substrates with high surface density and coverage, including silicon (Si), glass, polydimethylsiloxane (PDMS), and copper (Cu) sheets, as well as Si seeded with ZnO nanocrystals. Time-resolved SEM revealed growth kinetics of the ZnO nanostructures on Si, capturing the emergence of “infant” urchins at the early growth stage and subsequent progressive increases in the urchin nanoneedle length and density, whilst the spiky nanoneedle morphology was retained throughout the growth. ε-Zn(OH)2 orthorhombic crystals were also observed alongside the urchins. The crystal structures of the nanostructures at different growth times were confirmed by synchrotron X-ray diffraction measurements. On seeded Si substrates, a two-stage growth mechanism was identified, with a primary growth step of vertically aligned ZnO nanoneedle arrays preceding the secondary growth of the urchins atop the nanoneedle array. The antibacterial, anti-reflective, and wetting functionality of the ZnO urchins—with spiky nanoneedles and at high surface density—on Si substrates was demonstrated. First, bacteria colonization was found to be suppressed on the surface after 24 h incubation in gram-negative Escherichia coli (E. coli) culture, in contrast to control substrates (bare Si and Si sputtered with a 20 nm ZnO thin film). Secondly, the ZnO urchin surface, exhibiting superhydrophilic property with a water contact angle ~ 0°, could be rendered superhydrophobic with a simple silanization step, characterized by an apparent water contact angle θ of 159° ± 1.4° and contact angle hysteresis ∆θ < 7°. The dynamic superhydrophobicity of the surface was demonstrated by the bouncing-off of a falling 10 μL water droplet, with a contact time of 15.3 milliseconds (ms), captured using a high-speed camera. Thirdly, it was shown that the presence of dense spiky ZnO nanoneedles and urchins on the seeded Si substrate exhibited a reflectance R < 1% over the wavelength range λ = 200–800 nm. The ZnO urchins with a unique morphology fabricated via a simple route at room temperature, and readily implementable on different substrates, may be further exploited for multifunctional surfaces and product formulations.

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