Transport mechanisms of polysulfides (PS), Li+ and electrolyte through nanochannels are not yet fully understood, limiting the design of nanostructured separators aimed at blocking the PS shuttle ...effect in lithium-sulphur batteries. Herein, Carbon Nanotubes (CNTs) with diameters calibrated to the minimal cross-section of soluble LiPS were used as models of hydrophobic nanochannels. Reservoirs containing different concentrations of lithium salts were separated by CNTs, then concentration gradient and electric-field driven Molecular Dynamics were performed. The various virtual experiments show that neither PS nor Li+ permeate through CNTs with diameters of 1.5 and 2.0 nm and, as corroborated by free energy calculations, the ions prefer to enter into the nanotubes forming ion pairs, possibly larger ion aggregates, when the required energy is supplied. By increasing the diameter to 4 nm, the electrolyte permeation changes dramatically from nearly frozen to bulk-like en masse transport, and a high polysulfides rejection was found. The PS density map inside this nanotube suggests a polysulfide adsorption on the CNT inner wall, which would minimize the shuttle effect while maintaining bulk-like electrolyte transport. This result derives from a trade-off between the diameter of the nanochannel and the wall hydrophobicity.
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•Molecular insights into ion transport mechanisms in CNT-based nanochannels.•Effects of nanochannel diameter on polysulfide rejection and lithium permeation.•Li2S6 rejection and Li permeation unveiled by Molecular Dynamics experiments.•En masse Li diffusion and confinement effect predicted by in-silico experiments.
A novel ternary rGO/PPy/S nanocomposite possessing of a hierarchical nanostructure via incorporating the matrix of reduced graphene oxide (rGO) coated by polypyrrole (PPy) with sulphur was prepared ...by a facile one-pot in situ method. The chemical bonds exist between PPy and rGO through the formation of graphitic N and pyridine oxide N, and the CS, SC=S and SO chemical bonds form between rGO/PPy and S in the structure of the rGO/PPy/S material. The loading content of sulphur is 69.43wt.% for the rGO/PPy/S sample. The rGO/PPy/S material exhibits a high performance when used as the cathode of Li-S battery. The initial and last discharge capacity arrived at 991.5 and 626.7mAhg−1 at 1C with 400 cycles which is corresponding to the capacity retention ratio of 63.2%, indicating its very high cyclic stability. The discharge capacity of 537.4mAhg−1 could be obtained at 5C and it maintained at 442.1mAhg−1 after 400 cycles with the Coulombic efficiency of more than 90%, showing its excellent rate stability.
Lithium-sulphur battery technology promises much higher energy storage capacity compared to common Li-ion commercial batteries. Li–S batteries have high theoretical capacity of 1672 mAh g−1, thanks ...to conversion reaction from solid sulphur to lithium polysulfides (LiPSs). Unfortunately, few issues are still hindering their commercialization. The main problem afflicting lithium sulphur batteries is the shuttle phenomenon, due to soluble long chain LiPSs generated at the cathode. In the last years, many interlayer separators have been based on materials showing physical blocking of LiPSs. In particular, MoS2 and PANI separately showed strong adsorption capability, preventing polysulfides dissolution and accelerating the redox reaction kinetics. In the present work we rationally design, for the first time, composite materials based on PANI and MoS2, with the aim to evaluate the specific role of each component and their synergy as LiPSs blocking-agents, by implementation of a second layer containing the MoS2/PANI composite directly on the top of the standard S/C electrode. The systematic study confirms that double-layer containing the composite remarkably improves the performance of the sulphur cathode, showing specific capacity close to 600 mAh g−1, which is 42% higher than the standard sulphur cathode, after 500 cycles.
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•Systematic study evaluating synergy of PANI and MoS2 for LiPSs trapping.•Double-layer implementation and optimization directly on sulphur cathode.•Syntheses carried out keeping in mind the feasibility of industrial scale-up.•Promising electrochemical performances for long-time cycling.•Performances correlated to the conductive pathway and the catalytic effect.
This work is to study the reasons for the relatively low efficiency of sulphur reduction (about 75%) in lithium-sulphur batteries. The two main reasons for that are suggested to be: the relatively ...low electrochemical activity of low order lithium polysulphides and blocking of the carbon framework of the sulphur electrode by insoluble products of electrochemical reactions - sulphur and lithium sulphide. The electrochemical activity of lithium polysulphides with different composition (Li sub(2)S sub(n), n = 2-6) has been studied in 1 M solutions of CF sub(3)SO sub(3)Li in sulfolane. It is shown that lithium polysulphides including lithium disulphide are able to electrochemically reduce with efficiency close to 100%. The electrochemical activity of lithium polysulphides decreases with the order. The order of lithium polysulphides affects the value of voltage of discharge plateaus but not the efficiency of sulphur reducing in the lithium polysulphides species. The relatively low efficiency of sulphur reduction in the lithium-sulphur batteries is more likely caused by blocking of carbon particles in the sulphur electrode by insoluble products of electrochemical reactions (sulphur and lithium sulphide). This prevents the electrochemical reduction of low order lithium polysulphides and especially lithium disulphide.
Semi-interpenetrated network Solid Polymer Electrolytes (SPEs) were fabricated by UV-induced cross-linking of poly(ethyleneglycol) diacrylate (PEGDA) and divinylbenzene (DVB) within a ...poly(ethyleneoxide) (PEO) matrix (Mv=5×106gmol−1), comprising lithium bis(trifluoromethanesulfonyl)imide salt (LiTFSI), at a molar ratio of EO:Li ∼30:1. The influence of the DVB content on the final SPE properties was investigated in detail. An increase of DVB concentration resulted in self-standing polymer electrolytes. The DVB cross-linker incorporation was found to decrease the crystallinity of the PEO matrix from 34% to 23%, with a decrease in the melting temperature (Tm) of the membrane from 50°C to 34°C. Moreover, the influence of the DVB concentration on the ionic conductivity was determined for polymer electrolytes with 0, 10, 20 and 45% DVB from room temperature (RT) to 80°C. The resulting SPEs showed a high electrochemical stability of 4.3V as well as practical conductivity values exceeding 10−4Scm−1 at 70°C. Cycling performance of these semi-interpenetrated SPE’s have been shown with a Li metal polymer battery and all solid -state Li sulphur battery.
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•Polar and conductive titanium carbide is introduced for redox regulation.•Lithium sulfide plays as sulfur source in this study.•Sulfur redox and lithium sulfide precipitation are ...remarkably promoted.•The electrochemical characteristics of as-prepared batteries are boosted.
The lithium-sulfur batteries (LSBs) have attracted more and more attention in recent years owing to its high theoretical energy density, abundant sulfur source and relatively low cost. However, the serious polysulfides shuttle and sluggish sulfur redox kinetics hinder the development and commercial application of high-performance lithium-sulfur batteries. In this paper, the titanium carbide (TiC)-decorated carbon matrix is considered as the mediator, anchor and electrocatalyst for polysulfides redox reaction. It has been proved that the conductive and polar titanium carbide can not only chemisorbs lithium polysulfides via titanium-sulfur (Ti-S) coordination, but also optimize the lithium sulfide (Li2S) nucleation/precipitation mechanism for better redox reaction. Especially, the graphene oxide and carbon nanotube matrix (GO-CNT) in this case can act as both host for Li2S loading and TiC precipitation. Accordingly, the as-fabricated lithium sulfide-graphene oxide–carbon nanotube-titanium carbide (LS-GO-CNT-TiC) cathode delivers the high initial discharge capacity of 956 mAh g−1 at 0.1C and good rate capability of 508 mAh g−1 at 2C. These results consequently manifest that the conductive and polar matrix of LS-GO-CNT-TiC can perform as a promising cathode of the high performance LSBs.
Nanosheet structures of copper oxide@graphene oxide (CuO@GO) composite were developed as a host material to embed sulphur nanoparticles for use as cathodes in lithium–sulphur (Li–S) batteries. The ...homogeneous immobilisation of sulphur in the conductive matrix of CuO@GO within a strong chemical bond between carbon and polysulphide intermediates through the Lewis acid function of CuO provides a high specific discharge capacity of the CuO@GO/S electrode in comparison with the GO/S nanocomposite. The CuO@GO/S cathode delivers a discharge capacity of 1048.95 mA h g
-1
, 841.74 mA h g
-1
, 736.49 mA h g
-1
, 695.17 mA h g
-1
, 643.86 mA h g
-1
, and 457.08 mA h g
-1
at different current rates of 0.1 C, 0.4 C, 0.7 C, 0.8 C, 1 C, and 2 C, respectively. The application of CuO@GO/S maintains the average coulombic efficiency of 96 % after 300 cycles at 1 C rate with a capacity retention of approximately 55.8 %. The rapid ion transportation within the efficient physicochemical confinement of polysulphides confirmed the role of the CuO@GO/S nanocomposite as a promising cathode material for the next generation of high-energy density Li–S batteries.
Lithium-sulphur (Li-S) batteries offer high energy density compared to lithium-ion batteries, emerging as a promising technology for the next generation of energy storage systems. The ongoing ...challenge is to improve their electrochemical performance, extend their useful life and mitigate some problems that persist in this technology, by the investigation in materials with diverse properties. This work seeks to elucidate the importance and repercussions associated with functionalisation of graphene-based materials through nitrogen incorporation (more than 9 wt.% N), employing different chemical agents such as ethylenediamine and ammonia. Herein, differences in both the textural properties and the chemical environment of nitrogen within the carbonaceous network are identified, resulting in distinct electrochemical behaviours. The electrochemical performance of electrodes prepared from ammonia-functionalised samples surpasses that of ethylenediamine-functionalised samples in terms of both efficiency and rate performance. Conversely, the ethylenediamine-functionalised samples excel in stability, showing exceptional values in capacity retention per cycle. The outcomes exceeded expectations in energy performance, allowing the Li-S cells to be subjected to ultra-high rate cycling while maintaining appropriate capacity values.
Two new alkaline earth metal-organic frameworks (AE-MOFs) containing Sr(II) (
) or Ba(II) (
) cations and extended tetrahedral linker (MTA) were synthesized and characterized in detail (UPJS stands ...for University of Pavol Jozef Safarik). Single-crystal X-ray analysis (SC-XRD) revealed that the materials are isostructural and, in their frameworks, one-dimensional channels are present with the size of ~11 × 10 Å
. The activation process of the compounds was studied by the combination of in situ heating infrared spectroscopy (IR), thermal analysis (TA) and in situ high-energy powder X-ray diffraction (HE-PXRD), which confirmed the stability of compounds after desolvation. The prepared compounds were investigated as adsorbents of different gases (Ar, N
, CO
, and H
). Nitrogen and argon adsorption measurements showed that
has
area of 1321 m
g
(Ar) / 1250 m
g
(N
), and
does not adsorb mentioned gases. From the environmental application, the materials were studied as CO
adsorbents, and both compounds adsorb CO
with a maximum capacity of 22.4 wt.% @ 0 °C; 14.7 wt.% @ 20 °C and 101 kPa for
and 11.5 wt.% @ 0°C; 8.4 wt.% @ 20 °C and 101 kPa for
. According to IAST calculations,
shows high selectivity (50 for CO
/N
10:90 mixture and 455 for CO
/N
50:50 mixture) and can be applied as CO
adsorbent from the atmosphere even at low pressures. The increased affinity of materials for CO
was also studied by DFT modelling, which revealed that the primary adsorption sites are coordinatively unsaturated sites on metal ions, azo bonds, and phenyl rings within the MTA linker. Regarding energy storage, the materials were studied as hydrogen adsorbents, but the materials showed low H
adsorption properties: 0.19 wt.% for
and 0.04 wt.% for
@ -196 °C and 101 kPa. The enhanced CO
/H
selectivity could be used to scavenge carbon dioxide from hydrogen in WGS and DSR reactions. The second method of applying samples in the area of energy storage was the use of
as an additive in a lithium-sulfur battery. Cyclic performance at a cycling rate of 0.2 C showed an initial discharge capacity of 337 mAh g
, which decreased smoothly to 235 mAh g
after 100 charge/discharge cycles.
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