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Among various energy storage devices, lithium-sulfur batteries are the most promising candidate due to their high energy density and low cost. Polysulfide migration is a severe problem to inhibit the wide application of lithium-sulfur batteries. The efficient polysulfide inhibition is a determining factor for the high electrochemical performance of lithium-sulfur batteries. Therefore, the development of suitable host materials can inhibit that polysulfide inhibition has become a hot topic of research. Herein, we propose that the C/MoS2 composites can be used as sulfur host to catalyze the polysulfide conversion to improve the cycle stability of lithium-sulfur batteries. Thanks to the presence of the C/MoS2 host, the as-prepared C/MoS2@S cathode exhibits high capacity even at high rate of 5 C. This work provides direct evidence for the catalytic effect of C/MoS2 for accelerating polysulfide conversion kinetics. [ABSTRACT FROM AUTHOR]

Copyright of Rare Metals is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Metal phosphides fabricated using metal organic frameworks (MOF) have recently been widely studied in lithium-sulfur (Li–S) battery because of the unique microstructure and electrocatalytic activity. However, the growth of MOF is very rapid and the particle size mainly focuses on micrometer, which severely limits the catalytic effect. Herein, we fabricate nanoscale MOF embedded with carbon nanotube (CNT), owing to the ultra-small CoP (25 nm, denoted as S-CoP) derived from the phosphating of MOF and unique network of CNT, the designed micro-nano structure S-CoP/CNT accelerates the conversion of lithium polysulfides (LiPSs), boosts the precipitation/decomposition processes of lithium sulfide (Li2S) and provides an effective adsorption barrier. Meanwhile, the fabricated S-CoP/CNT separator endows an ultralong dendrite-free Li deposition up to 1714 h. The Li–S battery with S-CoP/CNT modified separator can deliver an initial capacity of 1513.22 mAh g−1 at 0.1 °C, a reversibility capacity of 574.95 mAh g−1 up to 500 cycles at 0.5 °C. The satisfactory performance is also verified at a high sulfur loading of 4.2 mg cm−2 and a favorable initial capacity of 1161.8 mAh g−1 can be maintained. This study provides a facile strategy to fabricate nano metal phosphides derived from MOF for Li–S battery. [ABSTRACT FROM AUTHOR]

The combination and structural regulation of physical adsorption and chemisorption carriers for polysulfides play an important role in limiting the shuttle effect of lithium-sulfur batteries (LSBs). So, in this paper, N, Co co-doped moss-like porous biochar (Co–N/CWPC) is synthesized and used as the sulfur host for LSBs. A large number of pores in the "moss" provide space for sulfur storage and volume expansion. And the introduction of N, Co provides plentiful catalytic adsorption sites, which can not only effectively limit the shuttle of polysulfides but also accelerate the conversion rate of polysulfides to the final discharge products. Moreover, Co also promotes graphitization and improves electrical conductivity of the biochar. After sulfur injection, the electrode shows an initial capacity of 787 mAh g−1 at 0.5 C and maintaining a capacity of 500 mAh g−1 after 500 cycles, the capacity decay rate is 0.07%. Even at a discharge rate of 1.0 C, it still maintained a capacity of 373 mAh g−1 after 1000 revolutions, with a capacity decay rate of 0.04%. [ABSTRACT FROM AUTHOR]

Highlights: The electrochemical principles/mechanism of Li–S batteries and origin of the shuttle effect have been discussed. The efficient strategies have been summarized to inhibit the shuttle effect. The recent advances of inhibition of shuttle effect in Li–S batteries for all components from anode to cathode. Lithium–sulfur (Li–S) batteries are supposed to be one of the most potential next-generation batteries owing to their high theoretical capacity and low cost. Nevertheless, the shuttle effect of firm multi-step two-electron reaction between sulfur and lithium in liquid electrolyte makes the capacity much smaller than the theoretical value. Many methods were proposed for inhibiting the shuttle effect of polysulfide, improving corresponding redox kinetics and enhancing the integral performance of Li–S batteries. Here, we will comprehensively and systematically summarize the strategies for inhibiting the shuttle effect from all components of Li–S batteries. First, the electrochemical principles/mechanism and origin of the shuttle effect are described in detail. Moreover, the efficient strategies, including boosting the sulfur conversion rate of sulfur, confining sulfur or lithium polysulfides (LPS) within cathode host, confining LPS in the shield layer, and preventing LPS from contacting the anode, will be discussed to suppress the shuttle effect. Then, recent advances in inhibition of shuttle effect in cathode, electrolyte, separator, and anode with the aforementioned strategies have been summarized to direct the further design of efficient materials for Li–S batteries. Finally, we present prospects for inhibition of the LPS shuttle and potential development directions in Li–S batteries. [ABSTRACT FROM AUTHOR]

Principles of inexpensive biotechnology are being increasingly used to address the problems posed by the use of lithium-sulfur batteries. We used chitin, a low-cost marine biowaste product, as a precursor for the in-situ preparation of chitin-derived nitrogen-doped hierarchical porous carbon fibers (CNHPCFs) containing abundant pores. These materials are characterized by varying morphologies and high specific surface areas and present a hierarchical porous structure. CNHPCFs adsorb polysulfides, exhibit good ionic conductivity, and can be potentially used to generate green energy. These properties help address the problems of volume expansion and slow transport. The CNHPCF-1@S cathode exhibits excellent cycling performance and high capacity (1368.80 mAh·g−1 at 0.2 C; decay rate: 0.011% per turn at 5 C). The high electrochemical reversibility recorded for CNHPCF-1@S and the stepwise reaction mechanism followed were studied using the in-situ X-ray diffraction and in-situ Raman spectroscopy techniques. The results reported herein can potentially help develop new ideas for the recycling and treatment of marine biofertilizers. The results can also provide a platform to improve the application prospects of lithium-sulfur batteries. [ABSTRACT FROM AUTHOR]

It was known that mesoporous metal-organic frameworks (MOFs) with hierarchical pores and unsaturated metal sites can effectively inhibit the shuttle effect of lithium polysulfides in lithium-sulfur battery, however, the unsatisfactory structural stability and electrical conductivity limit the application of mesoporous MOFs (MMOFs) in Li-S batteries. Aiming at sensible solutions, the conductive polyaniline (PANI) was incorporated into the MMOF to enhance the discharge capacity and the cycling stability of proposed Li-S batteries, as the stability and the conductivity of the MMOF cathode was improved simultaneously. The activated MMOF-PANI provides physical and chemical adsorption of polysulfides against their shuttle effect. Moreover, the introduction of PANI into the channels of MMOF effectively improves the conductivity of MMOF, thus improving the electrochemical performance of the MMOF-PANI-based batteries. Benefiting from these synergetic effects, the S@MMOF-PANI cathode delivers improved electrochemical performance including excellent rate performance and cycling stability. The battery shows an initial capacity of 777.7 mAh·g−1 at 2.0 C and a low decay rate of 0.06% per cycle in 1,000 cycles and approximately a repeatable rate performance. [ABSTRACT FROM AUTHOR]

The practical applications of lithium-sulfur (Li-S) batteries are limited by the low conductivity of sulfur and the shuttle effect of soluble polysulfides during the charge-discharge process. At the same time, biomass-based carbon materials have been acknowledged as the cost-effective and direct settlement to mitigate or overcome these problems due to their renewability, facile processing, and pollution-free characteristics. Therefore, in this work, we report the natural nori-based CoO nanoparticles decorated hierarchical porous carbon (HPC) for high-capacity Li-S battery cathodes. The HPC with an extremely high surface area of 2089 m2 g−1 provides a good substrate for the accommodation of CoO nanoparticles, which can effectively seize the lithium polysulfides and facilitate their redox conversion. As a result, the CoO-HPC/S cathode exhibits a high discharge capacity of 1557.1 mA h g−1, as well as excellent rate performance and cycling stability. Due to the naturally abundant nori-based cathode materials, the resultant Li-S battery is supposed to be an attractive and sustainable energy storage device. [ABSTRACT FROM AUTHOR]

Lithium-sulfur (Li-S) batteries are a promising electrochemical energy storage device due to their low cost, high energy density, and excellent sustainability, making them superior to many commercial lithium-ion batteries. Despite the great road to market, Li-S batteries still suffer from low practical energy density, which is intimately related to fundamental scientific and technological issues of sulfur cathodes. As a non-negligible parameter in sulfur cathodes, the compaction density plays a crucial role in the energy density of Li-S batteries. Herein, the effect of compaction density of sulfur/carbon cathodes on the electrochemical performance of Li-S batteries is investigated. It is demonstrated that sulfur/carbon cathodes with an optimized compaction density of 1.2 g cm−3 not only can guarantee the good contact of active materials, but can also ensure the rational dosage of electrolyte, thereby increasing the sulfur utilization as well as reducing the dissolution of polysulfide into the electrolyte. As a result, the pouch cells paired with the sulfur/carbon cathode and Li metal anode deliver superior specific capacity and remarkable cycling performance, which is attributable to the better contact between particles and the faster redox kinetics. This work reveals the contribution of the compaction density of the sulfur cathode to the electrochemical performance of the Li-S battery, providing an instructive paradigm for the rational design of an advanced sulfur cathode for large-scale commercialized Li-S pouch cells. [ABSTRACT FROM AUTHOR]

A better understanding of the redox process of lithium polysulfide (LPS) on carbon surfaces is helpful for designing Li/S batteries with better performance. The "shuttle mechanism" can explain the low coulomb efficiency and self-discharge of a Li/S battery, but it cannot explain the fact that battery performance is strongly affected by electrolyte volume and sulfur load. This paper aims to reveal the main redox process of LPS on the surface of carbon by examining the cathodic behavior with different electrolyte volume and sulfur load. Scanning electron microscopy (SEM) images and impedance spectra of the cathode before and after the first discharge were compared, and it was found that the discharge process is the continuous dissolution of sulfur composited with carbon into the electrolyte to form LPS. At the same time, LPS re-precipitates sulfur on the surface of the cathode through a disproportionation reaction to form a solid film. Cyclic voltammetry (CV) curves showed that the solid film passivates the electrode, and the electrode is activated only when the potential is swept negatively and Li2S is generated. When a lean electrolyte is used, there is fluctuation in the CV curves, which proves that the dissolution-reprecipitation of sulfur is the main process of the cathode. The discharge–charge curves of cathodes with different sulfur load were compared, and it was found that there is wavy fluctuation in the discharge curve when the sulfur load increases, which proves again that the sulfur reaction dominates the electrode process. [ABSTRACT FROM AUTHOR]

The shuttle effect of the polysulfide is a main bottleneck to hamper the wide application of the lithium-sulfur batteries. Therefore, it is important to inhibit the shuttle effect of the soluble polysulfide. In this work, a novel functional separator modified by MoO2 nanosheets (MONSs) is presented for overcoming this problem. Benefiting from the strong adsorption and catalytic activity of the MoO2 nanosheets, the polysulfide redox kinetics are greatly improved and the shuttle effect is also inhibited. Accordingly, the Li–S batteries with MONS-modified separator deliver high capacity of 1246 mAh/g at 0.05 C, perfect rate performance, and stable cycling performance. This work will open up great opportunities in the development of MoO2-modified separator for advanced Li–S batteries. [ABSTRACT FROM AUTHOR]

Copyright of Rare Metals is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Inductively-coupled thermal plasma processes were used to produce nanosized Li2S. Prior to the syntheses, the feasibility of forming Li2S was first evaluated using FactSage by considering the phase diagrams of sulfur and different lithium precursors in reducing atmospheres; Li2O, LiOH·H2O, Li2CO3 and Li2SO4·H2O all showed promises in producing Li2S nanoparticles, as confirmed by experiments. Argon and hydrogen mixtures were used as plasma gases, and a carbothermal reduction was implemented for Li2SO4·H2O. In addition, carbon-coated Li2S nanoparticles were synthesized with downstream injection of methane. Carbon was shown to stabilize Li2S upon contact with ambient air. The Li2S nanoparticles were electrochemically tested in half-cells using electrolytes containing LiNO3 or Li2S6 as additives. It was found that adding LiNO3 to the electrolyte was detrimental to the electrochemical performance of Li2S, whereas the combination of Li2S6 and LiNO3 as additives doubled the charge and discharge capacities of the half-cell over 10 cycles. [ABSTRACT FROM AUTHOR]

The large-scale manufacturing of lithium sulfur (Li-S) battery has been long hampered by the rapid capacity degradation and short cycle life, which is primarily attributed to the soluble polysulfides and subsequent continuing shuttling effect. The separator modification as a simple and effective technique has been extensively applied in Li-S batteries to solve inherent defects. Herein, the composite of Ketjen black (KB) and Ti4O7 was synthetized by carbothermal reduction and made into KB/Ti4O7-modified separator. The multifunctional layer can improve utilization of active substances and restrain shuttling effect by forming synergistic effect of physical obstruct and chemisorption for polysulides. The cell using KB/Ti4O7 separator exhibits enhanced electrochemical properties reflecting in higher specific capacity (1074 mAh g-1 at 1C) and longer cycling life (836 mAh g-1 after 100 cycles). The above results indicate that the composite of carbon and metallic oxide modified separator is pretty suitable for advanced Li-S battery. [ABSTRACT FROM AUTHOR]

Lithium-sulfur batteries have been studied as the promising energy storage device due to their high specific capacity and energy density. However, it is always a great challenge to solve the problems of the poor electronic conduction and severe shuttle effect of polysulfide. These two problems directly lead to low specific capacity and unstable cycling performance. To deal with this two issues, cobaltosic oxide nanospheres are developed and used as sulfur host materials in the lithium-sulfur batteries. Due to the efficient polysulfide adsorption and improved electronic conduction, the as-prepared Co3O4/S composites deliver high specific capacity and stable cycle performance. The initial specific capacity of the Co3O4/S electrode is about 1256 mAh g−1 at 0.1 C. [ABSTRACT FROM AUTHOR]

Various sulfur host materials have been developed to improve the performance of lithium-sulfur (Li-S) battery. In this work, we used phosphorus-doped graphitic carbon nitride (xP-g-C3N4) as a sulfur host material for the first time. xP-g-C3N4 was prepared with dicyandiamide as the precursor and 1-butyl-3-methylimidazole hexafluorophosphate as a phosphorus source. The effect of phosphorus doping on the electrochemical properties of xP-g-C3N4/S as cathode material for the Li-S battery was studied. The results show that decreasing lattice spacing improves the conductivity by doping phosphorus, and the specific surface area of 0.1P-g-C3N4 reaches 19.66 m2 g−1, which is about two times higher than that of g-C3N4. 0.1P-g-C3N4/S has 1344 mAh g−1 for the initial discharge specific capacity and 882 mAh g−1 for reversible specific capacity after 100 cycles with a capacity decay of 0.34% per cycle, exhibiting outstanding cycling performance and rate performance. Phosphorus-doped materials have a high specific capacity due to their own stronger physical adsorption and chemisorption of polysulfides and higher conductivity. This doping strategy proposed a new and efficient pathway for the fabrication of high-performance sulfur electrodes for Li-S batteries. [ABSTRACT FROM AUTHOR]

The practical application of the Li-S battery is restrained by the severe lithium polysulfide shuttle and sulfur insulation. In this work, the hollow V2O5 nanospheres wrapped by activated carbon as the host material for sulfur were prepared. The results indicate that initial specific discharge capacity of the electrode is 972 mA h g−1 and it can be maintained at 730 mA h g−1 after 200 cycles at 0.2 C. The average decay rate of the capacity for the AC@V2O5/S only is 0.09% per cycle after 200 cycles at 0.5 C. This excellent performance could result from the polar hollow V2O5 nanospheres providing more adsorption sites, which are conducive to electrolyte diffusion and confine polysulfides during the reaction of sulfur and polysulfide. Furthermore, the activated carbon coated on the outer layer can provide the large specific surface as conductive network. Therefore, this design strategy could show significant prospects for Li-S battery. [ABSTRACT FROM AUTHOR]

In order to solve the Li-S battery issues caused by the low conductivity of sulfur and the shuttle effect of lithium polysulfides, we successfully developed a spray drying method to prepare graphene oxide (GO) coating Ketjen Black@S composite powders, which is similar to the core-shell structure. The effects of different GO coating content on the battery performances were carefully studied. The results of the electrochemical measurements demonstrate that the 10% GO coating samples showed the best performances. With a high sulfur areal density of 3 mg cm−2, the 10% GO@KB-S cathode shows the highest discharge capacities of 1170.6 mAh g−1 at 0.05 C, 1010.0 mAh g−1 at 0.1 C, 880.1 mAh g−1 at 0.3 C, and 782.8 mAh g−1 at 0.5 C. Furthermore, the cycle retention of the 10% GO coating sample is 77.82% after 100 cycles and 71.13% after 200 cycles with the average coulombic efficiency of approximately 98%. [ABSTRACT FROM AUTHOR]

Herein, sulfur-/nitrogen-doped graphene (SNG) binary composite has been prepared by melt diffusion method and employed as cathode material for lithium-sulfur (Li-S) battery. The physical and electrochemical performances of prepared SNG binary composite were characterized using x-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscope, cyclic voltammetry and galvanostatic charge–discharge test. The SNG cathode delivers a high initial discharge capacity of 1135 mAh g−1, and it sustains the capacity of 687 mAh g−1 over the 50th cycle at 0.1C rate. The good electrochemical performance of SNG cathode is accredited to N-doping in graphene, which provides faster charge transfer pathway and suppresses the shuttle effect of polysulfides. The present study determines that the prepared SNG composite is a suitable material for cathode in Li-S battery application. [ABSTRACT FROM AUTHOR]

Practical application of Li-S battery is limited by the fast capacity decay and low coulombic efficiency caused by the shuttling phenomenon. Modification of the battery separator to impart the separator with ionic sieving property is an effective strategy to alleviate the shuttling phenomenon. In this study, perfluorinated sulfonic acid (PFSA) ionomers with different equivalent weight (EW) values are used to modify the commercial polyethylene separator, and the electrochemical performance of these separators is systematically investigated. Our results show that the separator modified using PFSA ionomer with a low EW value of 830 shows optimal battery performance owing to its unique structure of the ionic cluster. The Li-S battery with this modified separator shows an initial discharge capacity of 1352 mAh g−1 and a retained capacity of 931.6 mAh g−1 after cycling 100 times at 0.2 C, which demonstrates the effectiveness of this modification strategy. Furthermore, the correlation between the properties of PFSA ionomers and the electrochemical performance of the modified separator unveiled in this study may provide insight for the rational design of advanced separator for battery applications. [ABSTRACT FROM AUTHOR]

Li–S batteries are considered as candidates for the next-generation secondary batteries due to their high energy density (~ 1672 mAh g−1). However, poor conductivity and shuttle effect have become the major obstacles for their development. In the present investigation, we prepared porous biochar-coated metal nanoparticles CoFe@NC/PPC by loading the Prussian blue analogues onto the biomass pomelo peel (PP), followed by calcination. Both rich nitrogen-doped pore structure and CoFe nanoparticles can reduce the shuttle effect in the cycle, and biochar can enhance the conductivity of the sulfur cathode, promoting the complete reaction of sulfur. It is found that after being sulfur-injected and made into a button cell, it exhibits good electrochemical performance. The initial specific capacity was found to be close to 915.6 mAh g−1 at 1 C and it remained at 447.4 mAh g−1 after 500 cycles with a coulombic efficiency of 97.3%. [ABSTRACT FROM AUTHOR]

Activated porous carbons originating from the Indonesian snake skin fruit peel has been prepared by carbonization process followed by the ZnCl2 activation process. This porous carbon was then applied as cathode component along with sulfur in lithium sulfur (Li–S) batteries. The carbon materials possessed a high surface area of 2247 m2 g−1 and a large pore volume of 1.97 cm3 g−1 with sulfur loading of 63%. From the x-ray diffraction (XRD) patterns, Raman analysis, and SEM observation of the composites, it was shown that the sulfur was uniformly encapsulated inside the carbon pores, which was beneficial for the optimum utilization of sulfur and the confinement of soluble lithium polysulfides. The fabricated carbon-sulfur composite electrodes demonstrated an initial specific capacity of 945 mAh g−1 and good capacity retention until the 100th cycle at 0.1 C rate. At high C rate (1 and 2 C), the composite electrodes exhibited specific discharge capacity of 538 and 466 mAh g−1 until the 100th cycle, respectively. Those excellent electrochemical performances were attributed to the high surface area, combination of micropore/mesopore structures and low average pore diameter of porous carbons. [ABSTRACT FROM AUTHOR]

Due to the introduction of porous carbon and rational design of cathode structure, the shuttle effect of polysulfide has been remarkably relieved. However, most reported carbon/sulfur composites exhibiting attractive performance are prepared through complex process, leading to a hard application in industry. Compared with a wide study on cathode material, relative few attentions have been paid on binder which is essential ingredient in cathode and play important role in enhancement of battery performance. Herein, we prepared novel binder (denoted as PAA-DA binder) through reaction of polyamic acid (PAA) and dopamine (DA). There are abundant carbonyl, acylamino, and hydroxide groups in the molecular structure of PAA-DA, which can form a strong interaction with the polysulfide, resulting in the alleviation of shuttle effect. The results of electrochemical test indicate that the PAA-DA binder effectively enhances the cycle stability of cathode at different current densities owning to the functional groups of PAA-DA significantly entrapping polysulfide through chemical interactions. Graphical abstract Schematic illustration of PAA-DA binder entrapping polysulfide [ABSTRACT FROM AUTHOR]

Graphene nanosheets are a promising scaffold to accommodate S for achieving high performance Li/S battery. Nanosheet activation is used as a viable strategy to induce a micropore system and further improve the battery performance. Accordingly, chemical activation methods dominate despite the need of multiple stages, which slow down the process in addition to making them tiresome. Here, a three-dimensional (3D) N-doped graphene specimen was physically activated with CO2, a clean and single step process, and used for the preparation of a sulfur composite (A-3DNG/S). The A-3DNG/S composite exhibited outstanding electrochemical properties such as an excellent rate capability (1,000 mAh·g−1 at 2C), high reversible capacity and cycling stability (average capacity ~ 800 mAh·g−1 at 1C after 200 cycles), values which exceed those measured in chemically activated graphene. Therefore, these results support the use of physical activation as a simple and efficient alternative to improve the performance of carbons as an S host for high-performance Li-S batteries. [ABSTRACT FROM AUTHOR]

In this study, cetyltrimethylammonium bromide (CTAB)-modified separator is developed by using a simple and facile method for lithium-sulfur (Li-S) batteries. CTAB is coated on only one side of separator using a doctor blade. The coated CTAB on the separator improves wettability between separator and electrolyte and ionic conductivity of separator. In addition, CTAB also inhibits the migration of dissolved polysulfides to the anode side. These phenomena improve the electrochemical properties of Li-S batteries using CTAB-coated separators. Cells using the CTAB-coated separator exhibit an initial capacity of 1136 mAh g−1 at 0.2 C-rate. In addition, they can maintain a higher capacity (765 mAh g−1) and capacity retention rate (67.3%) after 150 cycles as compared to pristine Li-S batteries (549 mAh g−1 and 48.5%, respectively). These results indicate that the CTAB-coated separator can enhance the performance of Li-S batteries.Graphical abstract: [ABSTRACT FROM AUTHOR]

S/TiO2 composite is prepared via a simple solution method by using sublimed sulfur and nanosized TiO2. The composite is characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) test. The results indicate that the sulfur is well dispersed in the composite. The electrochemical performance of the composite as cathode material was evaluated by cycling under constant current cyclic voltammetric (CC-CV) mode at room temperature and cyclic voltammetry (CV). The S/TiO2 composite can effectively confine the diffusion of dissolved polysulfides in electrolyte and stabilize the structure during the charge and discharge process and shows high capacity and good rate performance. [ABSTRACT FROM AUTHOR]

A mesoporous carbon (MC) is prepared by the method of hard-template. Cathode materials (S/MC) for Li-S battery were synthesized. Properties of S, MC, and S/MC were characterized by BET, XRD, Raman, HRTEM, and FESEM. Electrochemical performances of the batteries were determined by AC impedance, cyclic voltammetry, and constant-current charging and discharging. Experiments show that MC, prepared with mass ratio CaCO3/PVA = 1/1.5, is the most suitable for Li-S battery. Thereby, the battery shows initial specific capacity of 1383.6 mAh/g and 881.6 mAh/g after 100 cycles, and the Coulombic efficiencies are both over 98% after 100 cycles at the current rate of 0.5 and 1 C. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT) clusters grown in situ in three-dimensional (3D) porous graphene networks (3DG-CNTs), with integrated structure and remarkable electronic conductivity, are desirable S host materials for Li-S batteries. 3DG-CNT exhibits a high surface area (1,645 m·g), superior electronic conductivity of 1,055 S·m, and a 3D porous networked structure. Large clusters of CNTs anchored on the inner walls of 3D graphene networks act as capillaries, benefitting restriction of agglomeration by high contents of immersed S. Moreover, the capillary-like CNT clusters grown in situ in the pores efficiently form restricted spaces for Li polysulfides, significantly reducing the shuttling effect and promoting S utilization throughout the charge/discharge process. With an areal S mass loading of 81.6 wt.%, the 3DG-CNT/S electrode exhibits an initial specific capacity reaching 1,229 mA·h·g at 0.5 C and capacity decays of 0.044% and 0.059% per cycle at 0.5 and 1 C, respectively, over 500 cycles. The electrode material also reveals a remarkable rate performance and the large capacity of 812 mA·h·g at 3 C. [ABSTRACT FROM AUTHOR]

Li-S batteries are one of exciting new technologies in high energy density storage devices. But, their widespread commercialization has been limited by several obstacles. Elemental sulfur is not conductive electrically and electrochemical conversion during cycles causes intense change in volume. In this work, a sulfur/polyaniline/nitrogen-doped graphene aerogel (S@PANi-NGA) nanocomposite synthesized through a facile chemical procedure. Nitrogen-doped amino functionalized graphene aerogel (NGA) used as cross-linker for polyaniline to improve the stability of the entire cathode framework. Also, NGA possesses porous structure, high surface area, and enhances electronic conductance due to the nitrogen atoms doped into graphene sheets. As a result, S@PANi-NGA delivered an initial discharge capacity of 1332 mAh g at a scan rate of 0.2 C and 872 mAh g of the capacity retained after 100 cycles. The performance was clearly superior to the sulfur/PANi binary composite, in which pure polyaniline used as accommodator. [ABSTRACT FROM AUTHOR]

Hierarchical-structured copper sulfide nanoneedles were grown on multi-walled carbon nanotube backbone (denoted as CuS@CNT) as electrodes for supercapacitors via a facile template-based hydrothermal conversion approach and further by simply impregnating sulfur into CuS@CNT (S@CuS@CNT) as electrodes for Li-S batteries. The electrochemical measurements showed that the resultant CuS@CNT composite electrodes deliver outstanding electrochemical performance with a specific capacitance up to 566.4 F g and cyclic stability of 94.5 % of its initial capacitance after 5000 cycles at a current density of 1 A g. A synergistic effect arising from the unique hierarchical structure was responsible for the electrode performance, including a large surface area of 49.3 m g and active CuS ultrafine nanoneedles firmly bonded to the highly conductive carbon nanotube (CNT) backbone. When used as an electrode material for Li-S batteries, the S@CuS@CNT (S content 59 wt%) exhibited satisfying electrochemical performance. The S@CuS@CNT electrode showed that coulombic efficiency was close to 100 % and capacity maintained more than 500 mA h g with progressive cycling up to more than 100 cycles even at a high current density. This strategy of stabilizing S with a small amount of copper sulfide nanoneedles can be a very promising method to prepare free-standing cathode material for high-performance Li-S batteries. The fabrication strategy presented here is low cost, facile, and scalable, which can be considered as a promising material for large-scale energy storage device. In particular, the use of CNT as backbone for the growth of active materials presents many potential merits owing to its lightweight, biodegradable, and stretchable characteristics. [ABSTRACT FROM AUTHOR]

A sulfur cathode with enhanced electrochemical properties is prepared by a hydrogel binder owning three-dimensional polymeric network for Li-S batteries. The promising high-performance binder (Alg-Ca) is constructed by an in situ interconnection of alginate chains by additive divalent cation with a facile and self-assembly strategy. With the assistance of 3D network, the sulfur/activated carbon composite cathode exhibits a higher rate capability and cycling performance compared to poly(vinylidene fluoride) binder, and the capacity retention is up to 80.6 % after 200 cycles (0.5C, 1C = 1675 mA g). Additionally, the electrochemical impedance spectroscopy also reveals a lower electrode resistance and better kinetic characteristics with Alg-Ca as a binder. The improved electrochemical behaviors are assigned to the ability of maintaining the electrode stability due to the excellent mechanical property and amorphous structure. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A commercial carbon black with microporous framework is used as carbon matrix to prepare sulfur/microporous carbon (S/MC) composites for the cathode of lithium sulfur (Li-S) battery. The S/MC composites with 50, 60, and 72 wt.% sulfur loading are prepared by a facile heat treatment method. Electrochemical performance of the as-prepared S/MC composites are measured by galvanostatic charge/discharge tests, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), with carbonate-based electrolyte of 1.0 M LiPF/(PC-EC-DEC). The composite with 50 wt.% sulfur presents the optimized electrochemical performance, including the utilization of active sulfur, discharge capacity, and cycling stability. At the current density of 50 mA g, it can demonstrate a high initial discharge capacity of 1624.5 mAh g. Even at the current density of 800 mA g, the initial capacity of 1288.6 mAh g can be obtained, and the capacity can still maintain at 522.8 mAh g after 180 cycles. The remarkably improved electrochemical performance of the S/MC composite with 50 wt.% sulfur are attributed to the carbon matrix with microporous structure, which can effectively enhance the electrical conductivity of the sulfur cathode, suppress the loss of active material during charge/discharge processes, and restrain the migration of polysulfide ions to the lithium anode. [ABSTRACT FROM AUTHOR]

To improve the electrochemical performance of Li-S rechargeable batteries, tunable porous carbon materials, which are known as carbide-derived carbons (CDCs), are employed as adsorbents and conductive matrices for the cathodic sulfur materials. A new assembly for Li-S cells was developed by introducing multi-layer membranes as separators. The use of the multi-layer membranes enables the minimization of the shuttle effect by expanding the distance between the separators and blocking the penetration of the polysulfide. The best discharge capacity and cycle life were obtained with ten layers of PP membrane in a sulfur-CDC@1200 composite cathode, resulting in a discharge capacity of 670 mA h g and a minimal gap in the charge-discharge capacity during cell cycling. [ABSTRACT FROM AUTHOR]

The effect of adding a VO/carbon nano-composite to the cathode of a Li-sulfur battery on suppressing the polysulfide dissolution phenomenon was evaluated by comparing the amount of overcharge at the first discharge-charge processes. VO/carbon nano-composite was manufactured by forming VO ⋅HO xerogel on the carbon black through a simple wet process. This provides a high surface area with plenty of hydrophilic moieties that can capture and store soluble polysulfides on its surface during the discharge-charge reactions, and also partly contributes to suppressing the excessive formation of LiS which undergoes a large volume change during the cycling. From the electrochemical results, we could observe a significant reduction in the overcharge amount and improved cyclic performance by adding as little as 2 % of the nano-composite. UV-VIS spectra measured after a small addition of the nano-composite to the solution containing LiS polysulfide also confirmed that the VO/carbon nano-composite is highly effective in capturing long-chain polysulfides on its surface. [ABSTRACT FROM AUTHOR]

Abstract: Effective trapping of polysulfides within the carbon cathode host strongly depends on intrinsic C-S interactions. We report herein a systematic study of the influence of S-loading process on C-S interactions in MWCNT/S composites prepared by three commonly used industry-friendly methods, namely, mechanical solid-state mixing, infiltration method from a solution of S in CS2, and chemical deposition by disproportionation reaction of sodium sulfide and sodium thiosulfate. FESEM and TEM studies reveal strikingly different morphologies of the resulting MWCNT/S composites. XPS and Raman studies indicate different extents of recovery of π bonds in MWCNT due to varying degrees of C-S interfacial interactions in the composites. Furthermore, it is found that the C/O atomic ratio in the composites plays a crucial role: the higher the C/O value the better is the S-confinement. These subtle physical changes induced by C-S interactions in the composites can be related to electrochemical performance when tested in Li-S coin cells. It is found that the best results (high initial capacity of 1143 mAh g-1 and better capacity retention) could be achieved when the solution infiltration method was used for S-loading. This conclusion is further validated by using activated carbon as S-host.Graphical Abstract: SYNOPSIS MWCNT/sulfur composites with different S-loading methods have been investigated by XPS and Raman studies. The electrochemical performance in Li-S battery is correlated with different degrees of recovery of π bonds in MWCNT and the C/O atomic ratio in the composites due to a varying extent of C-S interactions. [ABSTRACT FROM AUTHOR]