Encapsulation Of Sulfur Research Articles

Synergistic Effect of Ni/TiO2 Heterostructures on Performance Enhancement of Lithium-Sulfur Batteries

Lithium-ion batteries (LIBs) opened new opportunities for rapid development of modern portable devices. LIBs use mainly the intercalation cathodes represented by transition metal oxides and phosphates as cathodes, which are incapable of fulfilling the requirements of electric vehicles and high energy storage systems due to their limited energy density (less than 400 W h kg-1). Moreover, intercalation type cathodes have several drawbacks associated with high cost of materials and safety issues which also limit their use in electric vehicles and large-scale power systems. Therefore, implementation of alternative systems with higher specific capacity, energy density and inexpensive sources is required to meet high demands. In this regard, lithium sulfur (Li-S) batteries are considered as one of the most promising energy systems due to high theoretical specific capacity, which results in a theoretical energy density of 2600 Wh kg−1[1]. Moreover, sulfur has low cost, considerably less environmentally impact and abundant resources [2]. However, the implementation of Li-S batteries is hindered due to several drawbacks such as low conductivity of sulfur, complicated redox reactions, shuttle of soluble intermediates (polysulfides, LiPS), dendrite growth on lithium anode and volumetric expansion of cathode upon reduction to Li2S2/Li2S which leads to structural degradation and lower the cycle life of batteries [3].The shuttle effect can be suppressed via encapsulation of sulfur into carbon matrices, synthesis of conductive sulfur composites with polymers, etc. In our recent works we reported on carbon materials with metal -oxides, -sulfides and -nitrides as sulfur immobilizers exhibiting strong affinity to LiPSs. Despite such strong immobilization effect of metal compounds, the conversion of sulfur to the end products needs to be enhanced by introduction of electrocatalysts. In this work, the synergistic effect of heterostructures with double functions, titanium dioxide as LiPSs immobilizer with Ni nanoparticles as electrocatalysts were prepared and analyzed as an effective sulfur host material.The present study focuses on the implementation of composite compounds with dual effects on the performance enhancement of Li-S batteries. Acknowledgements This research was funded by a research grant No. AP23490764 and BR21882402 from the Ministry of Science and Higher Education of the Republic of Kazakhstan. Figure 1

Electrochemical Responses of Solution-Impregnated Sulfur/Mesoporous Carbon Composites in Liquid Li-S and Solid-State Li-S Batteries

Lithium sulfur solid-state batteries (Li-S SSBs) have received great attention as next-generation sustainable energy storage devices due to their high energy density, low cost and potential safety. However, start-of-the-art Li SSBs have still faced a few serious of hinders such as distinct high interfacial impedance, insufficient sulfur utilization, lower sulfur mass loading, mismatch triple phase interfaces and also uncertain electrochemical mechanism between liquid and solid-state lithium sulfur batteries. Here, to address these concerns, we employed the encapsulation of sulfur into high conductivemesoporous carbon (MC) by combined solution impregnation and melt-diffusion techniques (IM) to prepare S@MC, and looked into their electrochemical responses in liquid (LiTFSI+LiNO3) and sulfide solid-state (LI6PS5Cl, LPSCl) electrolyte systems. The separately assembled liquid and solid-state Li-S cells exhibited initial discharge capacities of 1438 mAh g-1 and 1411 mAh g-1 at 0.1 C, and capacity retentions of 85.6% (at 0.5 C after 300 cycles) and 48.2% (at 0.5 C after 200 cycles), respectively. In order to enhance the long-term capacity retention of the Li-S SSB prepared by dry mixing of S and LPSCl, we tailored interfaces and introduced ploysulfido-intermediate compounds between S and LPSCl, and thus increasing intimate ionic contact through a weak polar solvent by wet mixing. The solid-state Li-S cells exhibited an initial discharge capacity of 1621 mAh g-1 at 0.1 C with capacity retention of 97.12% (0.1 C initial 5 cycles) and 58.53% (0.5 C after 200 cycles). This work evidently revealed that two step solid-liquid-solid and one step solid-solid charge transfer conversions followed for liquid and sulfide solid state electrolytes, respectively. The solution-impregnated S@MC-2-65%+LPSCl sulfur composite prepared by wet mixing could be potential candidate for high performance Li-S SSBs.

Polysulfide-mediating properties of nickel phosphide carbon composite nanofibers as free-standing interlayers for lithium-sulfur batteries.

Issues such as the polysulfide shuttle effect and sulfur loss challenge the development of high-energy-density lithium-sulfur batteries. To address these limitations, a tailored approach is introduced using nickel phosphide carbon composite nanofibers (Ni x P/C) with controlled surface oxidation layers. These nanofibers feature a hierarchical structure that leverages the benefits of nickel phosphide nanoparticles and a carbonaceous matrix to enable efficient sulfur encapsulation and suppress polysulfide diffusion. Comprehensive characterization and electrochemical testing reveal that Ni x P/C, when employed as interlayers in a cell with a bio-waste-derived carbon-based sulfur cathode, significantly enhance electrochemical performance by increasing charge-discharge capacities and reducing charge-transfer resistance. Post-mortem analyses further show effective polysulfide trapping and conversion on the cathode side, preventing their shuttle to the anode, which results in a remarkable cycle stability of up to 200 cycles at 2C with a high discharge capacity of about 800 mA h g-1. These findings confirm the potential of Ni x P/C to improve lithium-sulfur battery technologies and demonstrate their applicability in diverse lithium-sulfur cell configurations.

Sulfur Encapsulation into Carbon Nanospheres as an Effective Technique to Limit Sulfide Dissolution and Extend the Cycle Life of Lithium–Sulfur Batteries

Sulfur Encapsulation into Carbon Nanospheres as an Effective Technique to Limit Sulfide Dissolution and Extend the Cycle Life of Lithium–Sulfur Batteries

Construction of lignosulphonate-containing polymersomes and prospects for their use for elemental sulfur encapsulation

The renewable nature and natural origin of sulfite lignin (lignosulfonate) allow considering it as a potential raw material for the synthesis of valuable environmentally friendly polymer nanomaterials. To create them, a deep understanding of the relationship between the structure of the lignosulfonate macromolecule and the nature of intramolecular and intermolecular interactions is necessary, which would make it possible to control self-assembly processes and obtain nanostructures of specified sizes and morphology. The work discusses the structure formation processes occurring in the lignosulfonate – water – acetone system during the spontaneous formation of polymer nanostructures and submicrostructures. The electrostatic effects of sulfo groups and counterions under conditions of changing the medium polarity and their contribution to self-associations of lignosulfonates have been established. A state diagram was plotted for the ternary lignosulfonate – water – acetone system under conditions of induced phase separation at T = 298 K and under atmospheric pressure. The size and ζ-potential of these nanostructures and submicrostructures of lignosulfonates were estimated depending on the composition of the medium of their formation. The morphology of the resulting nanostructures and submicrostructures of lignosulfonates has been established. The vesicular nature of the aggregates (polymersomes) was confirmed, their shape being close to ideal spheroids with one hole, ranging in size from 40 to 500 nm. A multi-stage mechanism for the formation of lignosulfonate nanoassociates and submicroassociates is proposed. The encapsulating ability of our polymersomes with respect to elemental sulfur from the instant of its inception until the loss of aggregative and sedimentation stability was assessed. Lignosulfonate polymersomes can be recommended as additives to prevent the occluding effect of sulfur melts during hydrometallurgical processing of sulfide ores.

Encapsulation of sulfur in MoS2-modified metal-organic framework-derived N, O-codoped carbon host for sodium–sulfur batteries

Room-temperature sodium–sulfur batteries (RT Na-S) are promising energy storage systems with high energy densities and low costs. Nevertheless, drawbacks, including the limited cycle life and sluggish redox kinetics of sodium polysulfides, hinder their implementation. Herein, a heterostructure of MoS2 nanosheets coated on a metal–organic framework (MOF)-derived N, O-codoped flower-like carbon matrix (NOC) was designed as a sulfur host for advanced RT Na-S batteries. The NOC@MoS2 hierarchical host provided a sufficient space to guarantee a high sulfur loading and confinement for the volume expansion of sulfur during the charge/discharge process. According to first-principle calculations, the NOC@MoS2 composite exhibited metallic conductivity because electronic states crossed the Fermi level, which indicates that the introduction of NOC significantly improved the electronic conductivity of MoS2. Furthermore, electron transfer from MoS2 to the O-doped carbon sites was observed owing to the strong electronegativity of O, which can effectively increase the Lewis acidity of MoS2 and weaken the sodium–sulfur bonds in sodium polysulfides after adsorption on the cathode, leading to reductions in the Na2S dissociation energy barrier and Gibbs free energy for the rate-limiting step of the sulfur reduction process. Therefore, with the synthetic effects of MoS2 and N, O-codoped carbon, the obtained cathode exhibited a superior electrochemical performance.

Degradation Mechanisms of a Li—S Cell using Commercial Activated Carbon

<p>In lithium–sulfur (Li–S) batteries, encapsulation of sulfur in activated carbon (AC) materials is a promising strategy for preventing the dissolution of lithium polysulfide into electrolytes and enhancing cycle life, because instead of solid–liquid–solid reactions, quasi-solid-state (QSS) reactions occur in the AC micropores. While a high weight fraction of sulfur in S/AC composites is essential for achieving a high energy density of Li–S cells, the deterioration mechanisms under such conditions are still unclear. In this study, we report the deterioration mechanisms during charge–discharge cycling when the discharge products overflow from the AC. Analysis using scanning electron microscopy and energy-dispersive X-ray spectrometry confirms that the sulfur in the S/AC composites migrates outside the AC as cycling progresses, and it is barely present in the AC after 20 cycles, which corresponds to the capacity decay of the cell. Impedance analysis clearly shows that the electrical resistance of the S/AC composite and the charge-transfer resistance of QSS reactions significantly increase as a result of sulfur migration. On the other hand, the charge–discharge cycling performance under limited-capacity conditions, where the discharge products are encapsulated inside the AC, is extremely stable. These results reveal the degradation mechanism of a Li–S cell with micro-porous carbon and provide crucial insights into the design of a S/AC composite cathode and its operating conditions needed to achieve stable cycling performance.</p>

Pressure swings assisted encapsulation of sulfur into expanded graphite as cathode for lithium-sulfur batteries

Pressure swings assisted encapsulation of sulfur into expanded graphite as cathode for lithium-sulfur batteries

Stable High-Capacity Elemental Sulfur Cathodes with Simple Process for Lithium Sulfur Batteries.

Lithium sulfur batteries are suitable for drones due to their high gravimetric energy density (2600 Wh/kg of sulfur). However, on the cathode side, high specific capacity with high sulfur loading (high areal capacity) is challenging due to the poor conductivity of sulfur. Shuttling of Li-sulfide species between the sulfur cathode and lithium anode also limits specific capacity. Sulfur-carbon composite active materials with encapsulated sulfur address both issues but require expensive processing and have low sulfur content with limited areal capacity. Proper encapsulation of sulfur in carbonaceous structures along with active additives in solution may largely mitigate shuttling, resulting in cells with improved energy density at relatively low cost. Here, composite current collectors, selected binders, and carbonaceous matrices impregnated with an active mass were used to award stable sulfur cathodes with high areal specific capacity. All three components are necessary to reach a high sulfur loading of 3.8 mg/cm2 with a specific/areal capacity of 805 mAh/g/2.2 mAh/cm2. Good adhesion between the carbon-coated Al foil current collectors and the composite sulfur impregnated carbon matrices is mandatory for stable electrodes. Swelling of the binders influenced cycling retention as electroconductivity dominated the cycling performance of the Li-S cells comprising cathodes with high sulfur loading. Composite electrodes based on carbonaceous matrices in which sulfur is impregnated at high specific loading and non-swelling binders that maintain the integrated structure of the composite electrodes are important for strong performance. This basic design can be mass produced and optimized to yield practical devices.

Covalent sulfur/CoS2-decorated honeycomb-like carbon hierarchies for high-performance sodium storage with ultra-long high-rate cycling stability

Transition metal sulfides (TMSs) with high theoretical sodium storage capacity have been regarded as one of the most competitive and promising anode materials for sodium-ion batteries. Nevertheless, great challenges still exist for TMS to achieve long-cycle life owing to the poor conductivity and volume expansion during the sodiation/desodiation process. The conventionally used pure carbon coating method can effectively solve the above problems. However, the low sodium ion storage capability of carbon will decrease the capacity of the anode. Thus the functionalization of well-designed carbon nanostructures with exotic elements (e.g., sulfur) or high-specific-capacity materials has been regarded as an efficient route to enhance sodium storage performance. Herein, we developed a facile strategy to incorporate covalent sulfur and CoS2 nanoparticles into honeycomb-like carbon matrices (denoted as S/CoS2@C), where sulfur is vaporized under vacuum and reacted with the Co-decorated carbon hierarchies, leading to the formation of CoS2 nanoparticles as well as the covalent C–Sx–C bonds. Consequently, the as-prepared S/CoS2@C composite demonstrates excellent sodium storage performance, with high initial coulomb efficiency (ICE) of 83 % and capacity retention of 95 % (478.5 mAh g−1) after 700 cycles at 0.2 A g−1, and an outstanding high-rate long-term cycling stability with a high reversible capacity of 396.1 mAh g−1 after 5000 cycles at 2 A g−1 (an average decay rate of only 0.0014 %). Furthermore, electrochemical analyses reveal that both covalent sulfur and CoS2 contribute to the sodium storage capacity via a predominantly surface-induced capacitive process, and the well-designed S/CoS2@C composite with encapsulation of covalent sulfur and CoS2 into the highly interconnected porous carbon matrices efficiently buffer the volume changes and well maintain the electrode integrity/conductivity upon sodiation/desodiation cycling.

Sustainable Synthesis of Sulfur-Single Walled Carbon Nanohorns Composite for Long Cycle Life Lithium-Sulfur Battery.

Lithium-sulfur batteries are considered one of the most appealing technologies for next-generation energy-storage devices. However, the main issues impeding market breakthrough are the insulating property of sulfur and the lithium-polysulfide shuttle effect, which cause premature cell failure. To face this challenge, we employed an easy and sustainable evaporation method enabling the encapsulation of elemental sulfur within carbon nanohorns as hosting material. This synthesis process resulted in a morphology capable of ameliorating the shuttle effect and improving the electrode conductivity. The electrochemical characterization of the sulfur-carbon nanohorns active material revealed a remarkable cycle life of 800 cycles with a stable capacity of 520 mA h/g for the first 400 cycles at C/4, while reaching a value around 300 mAh/g at the 750th cycle. These results suggest sulfur-carbon nanohorn active material as a potential candidate for next-generation battery technology.

Sulfur Encapsulation and Sulfur Doping Synergistically Enhance Sodium Ion Storage in Microporous Carbon Anodes.

MOF-based materials are a class of efficient precursors for the preparation of heteroatom-doped porous carbon materials that have been widely applied as anode materials for Na-ion batteries. Thereinto, sulfur is often introduced to increase defects and act as an active species to directly react with sodium ions. Although the sulfur introduction and high surface area can synergistically improve capacity and rate capability, the initial Coulombic efficiency (ICE) and electrical conductivity of carbon material are inevitably reduced. Therefore, balancing sodium storage capacity and ICE is still the bottleneck faced by adsorbent carbon materials. Here, sulfur-encapsulated microporous carbon material with nitrogen, sulfur dual-doping (NSPC) is synthesized by postprocessing, achieving the reduced specific surface area by encapsulating sulfur in micropores, and the increased active sites by edge sulfur doping. The synergy between encapsulation and sulfur doping effectively balances specific capacity, rate capability, and ICE. The NSPC material exhibits capacities of 591.5 and 244.2 mAh g-1 at 0.5 and at 10 A g-1, respectively, and the ICE is as high as 72.3%. Moreover, the effect of nitrogen and sulfur on the improvement of electron/ion diffusion kinetics is resonantly demonstrated by density functional theory calculations. This synergistic preparation method may reveal a feasible thought for fabricating excellent-performance adsorption-type carbon materials for Na-ion batteries.

Low-Cost Processing of Highly Durable (>1000 cycles) Sulfur Cathodes for Li-S Batteries

Lithium-sulfur (Li-S) batteries are one of the promising alternatives to modern Lithium-ion Battery (LIB) technology due to their superior specific energy density, which can satisfy the emerging needs of advanced energy storage applications such as electric vehicles and grid-scale energy storage and delivery. However, achieving this high specific energy density is hampered by several challenges inherent to the properties of sulfur and its discharge products.One major issue is related to the insulating nature of S and its fully discharged product (Li2S), which often leads to low utilization of the active material and poor rate capability. The poor electronic conductivity of these species can be overcome by utilizing conductive hosts, though they are dilutive and decrease the energy density, meaning that their mass ratio to the active material should be as low as possible [1]. Another crucial issue relates to the undesired solubility of certain sulfur discharge products, so-called long-chain Li polysulfides (LiPSs), in the conventional ether-based liquid electrolyte. The solubility of long-chain LiPSs promotes their free back-and-forth transport between the positive and negative electrodes, which results in poor cyclability and capacity decay [2, 3]. Despite the efforts to engineer and control the undesired LiPSs shuttling effect, advances have been mostly limited to a small number of cycles (100-200), or the need for complex and often expensive synthesis that has limited the rational development of new sulfur cathodes.At present, a large majority of the sulfur cathode research has focused on nano-architectured electrodes using 2D and 3D host materials for sulfur, such as carbon nanotubes, graphene, conductive scaffolds, yolk-shell structures, and the like, to increase the conductivity and alleviate the LiPSs shuttling [4]. Although these approaches have helped to increase the achievable capacity, and sometimes the cyclability, their synthesis methods have been highly complex, meaning that their manufacturing cost will be high. Also, in operating cells, it is highly unlikely that these complex structures can be effectively reproduced upon many charge-discharge cycles – meaning that capacity loss is essentially inevitable. Thus, developing novel, yet affordable and scalable, cathode architectures that can enhance the rapid transport of Li-ions to active sites for electrode reactions, accommodate discharge-induced volume expansion, and minimize the shuttling mechanism by sulfur encapsulation are still in great need.In this work, we present a low-cost and scalable processing method for highly durable sulfur cathodes containing commercial sulfur, carbon black, and polyvinylidene fluoride (PVDF). The sulfur cathode slurry was prepared through a simple and scalable recipe where the degree of binder dissolution into the solvent was controlled before electrode deposition. Variables such as the solvent:binder ratio, dissolution time, and agitation will be discussed. The microstructure of the sulfur cathodes was characterized using scanning electron microscopy. Through controlled dissolution of binder, a porous, swollen network of binder was achieved that adhered the sulfur and carbon particles while providing a highly porous structure that can accommodate the sulfur volume expansion during discharge and impede dissolution of the discharge products into the electrolyte by physically trapping them. The cycling performance of the sulfur cathodes prepared through the present novel processing was tested at C/10 and compared with those prepared through the conventional production techniques. The sulfur cathodes prepared with this novel electrode processing offered impressive capacity retention of 80% after 1000 cycles suggesting a considerable improvement in the shuttling effect and active material preservation. These results are expected to help move the production and manufacturing of Li-S batteries forward.References -J. Lee, T.-H. Kang, H.-Y. Lee, J. S. Samdani, Y. Jung, C. Zhang, Z. Yu, G.-L. Xu, L. Cheng, S. Byun et al., Advanced Energy Materials, vol. 10, no. 22, p. 1903934, 2020.Yang, G. Zheng, and Y. Cui, Chemical Society Reviews, vol. 42, no. 7, pp. 3018–3032, 2013.She, Y. Sun, Q. Zhang, and Y. Cui., Chemical society reviews, vol. 45, no. 20, pp. 5605-5634, 2016.Zhou, D. L. Danilov, R.-A. Eichel, and P. H. L. Notten, Advanced Energy Materials, vol. 1, p. 2001304, 2020.

Microstructural Evolution Revealed By Operando X-Ray Tomographic Microscopy in Next Generation Batteries

Sulfur conversion chemistry boasts a high theoretical specific capacity of 1672 mAh/gs and promises to deliver a high-energy density battery when combined with a lithium metal anode (3862 mAh/gLi). The use of such chemistries has the additional benefits of utilizing abundant and low cost materials in the cathode, i.e. carbon and sulfur.[1] Despite clear advantages, lithium-sulfur (Li-S) batteries still face a low practical energy density, poor rate performance, and limited cycling life. These issues are a result of the complex conversion chemistry of the cathode, and the stripping/plating mechanism of the Li-metal anode. These processes include the dissolution and diffusion of polysulfide species through the cell’s electrolyte from the cathode resulting in capacity fade, in addition to the growth of dendritic structures from the anode causing the formation of ‘dead lithium’ and short circuiting of the battery. A plethora of strategies have been developed to address the issues posed by the soluble polysulfide species, from using additives to prevent polysulfide shuttling, to encapsulation of sulfur to prevent its dissolution. While to address the growth of Li-dendrites, electrolyte formulations and the use of interlayer materials have been investigated.When developing these strategies, a detailed understanding of the conversion chemistry and Li-metal plating/stripping mechanisms during cycling is required. This can be obtained by e.g. the use of Raman spectroscopy to probe chemical changes to electrolytes and observe polysulfide speciation,[2] or using phase-field modelling to investigate factors that influence the growth mechanisms of Li-metal during plating.[3] In addition, sulfur dissolution and Li-metal dendrite growth induce microstructural changes that need to be probed using techniques with an appropriate resolution and field-of-view, e.g. synchrotron x-ray tomographic microscopy (XTM), which is capable of micrometre resolution, a near millimetre wide field of view, and measurement times of less than 60 seconds. This allows synchrotron XTM to continuously probe microstructural changes during battery operation, giving quantitative insights into the complex electrochemical mechanisms of the sulfur cathode and Li-metal anode.In this contribution we address the conversion processes of sulfur and its relation in limiting the battery’s practical specific capacity by using a capillary cell type battery, placing the entire cathode within the field of view of the XTM measurement. This enables quantification of the sulfur phase and correlative analysis with simultaneously acquired electrochemical data.[4] We demonstrate the full dissolution of elemental sulfur, with further conversion of sulfur species occurring immediately, and that an efficient diffusion of dissolved polysulfide species through and from the cathode is crucial to achieve a high specific capacity of Li-S cells in practice. Furthermore, we find that in the final step of cell discharge, a uniform and porous Li2S layer is formed on the cathode surface, effectively limiting access to the carbon surface and preventing further polysulfide conversion. We also demonstrate XTM as a unique technique to follow the growth of Li-metal microstructures in real time showing the difference in growth mechanisms when using different electrolyte compositions and under different cycling conditions. We observed change in the growth mechanisms of Li-metal. from homogenous mossy growth of Li-metal, to island dendritic growth and the formation of dead Li, to the growth of a globular phase, showing a changes in the fundamental process of Li-metal growth.[1] M. Agostini, J.Y. Hwang, H.M. Kim, P. Bruni, S. Brutti, F. Croce, A. Matic, Y.K. Sun, Adv. Energy Mater. 8 (2018) 1–7.[2] M. Sadd, M. Agostini, S. Xiong, A. Matic, ChemPhysChem 23 (2022).[3] Y. Liu, X. Xu, M. Sadd, O.O. Kapitanova, V.A. Krivchenko, J. Ban, J. Wang, X. Jiao, Z. Song, J. Song, S. Xiong, A. Matic, Adv. Sci. 2003301 (2021) 1–11.[4] M. Sadd, S. De Angelis, S. Colding‐Jørgensen, D. Blanchard, R.E. Johnsen, S. Sanna, E. Borisova, A. Matic, J.R. Bowen, Adv. Energy Mater. 2103126 (2022) 2103126.

A parametric study on encapsulation of elemental sulfur inside CNTs by sonically assisted capillary method: Cathodic material for rechargeable Li–S batteries

Encapsulation of elemental sulfur inside of carbon nanotubes is one of the best solutions to face the Lithium–Sulfur batteries challenges to get successful commercialization. In this work, the first parametric study of the capillary drawing-in dissolved materials in low surface tension solvents accompanying ultrasonic method is reported which has low heat consumption and convenient process. The optimized parameters are composite concentration (ratio of total composite material to solvent), ultrasonic irradiation power, ultrasonic irradiation time and initial sulfur concentration on the filling yield. A complete characterization were executed to investigate various characteristics of synthesized [email protected] composites. The results indicate that the elemental sulfur were successfully physically (no chemical bond) confined inside of the carbon nanotubes. The maximum amount of sulfur that confined inside the cavity of carbon nanotubes is 36.21 %wt. This synthesized composite as cathodic material for Li–S battery offers a stable cycling profile (81.68% capacity retention after 100 cycles at 2C) and sufficient capacity (725 mAh g−1 at 2C) at high C-rate. These results indicate that carbon nanotubes provide a high electronic conductivity shell with a cavity that balances the volume expansion of the sulfur during charge and discharge of cycles in Li–S batteries and also supplies an excellent trap for the polysulfides, prevents the dissolution of them, and controls the shuttle effect. These excellent results are believed to contribute to improvements in this technology.

Accurate determination of optimal sulfur content in mesoporous carbon hosts for high-capacity stable lithium-sulfur batteries

Mesoporous carbon materials have been widely used as hosts for sulfur encapsulation to mitigate the low electrical conductivity of sulfur, lithium polysulfide shuttle, and drastic volume changes of sulfur species associated with lithium-sulfur batteries (LSBs). The ideal sulfur-host composite should have an optimal content of sulfur that partially fills the pores of the host and produces the exact amount of final discharged product Li2S that can be completely accommodated by the pores of the host. However, accurately determining this optimal content of sulfur is a challenge and no effective method has been established. In this work, we successfully determined the optimal sulfur content for the Ketjenblack EC-600 JD (KB) sulfur host by simply characterizing sulfur-KB (SKB) composites with different sulfur contents using X-ray diffraction (XRD) spectroscopy coupled with thermogravimetric analysis (TGA). The LSB using the SKB with the optimal sulfur content of 52.9% showed a high specific capacity of 1535 mAh g−1 at 0.1C and a capacity of 680 mAh g−1 even at the high rate of 5C. Furthermore, it also showed stable cycling stability with low capacity decay rates of 0.05% and 0.09% per cycle over 500 cycles at 2C and 5C, respectively.

Covalent encapsulation of sulfur in a graphene/N-doped carbon host for enhanced sodium-sulfur batteries

Application of emerging room temperature sodium-sulfur (RT Na-S) battery is restrained by the poor conductivity, volume expansion of sulfur cathode and the shuttle effect of soluble polysulfides in electrolytes. Herein, an N-doped two-dimensional (2D) carbon host was derived from the polydopamine coated graphene for sulfur storage. Different from the conventional used melt-diffusion method to integrate sulfur on graphene layer physically, we employed a vapor-infiltration method to realize the homogenous incorporation of sulfur in the graphene-based host via C-Sx-C bond. A polydopamine-derived N-doped carbon layer was further coated on graphene to confine the high-temperature-induced gas-phase sulfur, which effectively increase the covalently bonded sulfur content in the host. Moreover, based on Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) measurement, the C-S bonds are mainly formed beside N-doped carbon, being well explained by the stronger interaction between N-doped carbon and S4 (sulfur vapor) than that of pure carbon from density functional theory (DFT) calculation results. When tested as a cathode for RT Na-S battery, the obtained N-doped graphene/sulfur cathode shows superior cycle stability.

Designing principles of advanced sulfur cathodes toward practical lithium‐sulfur batteries

Because the complicated design parameters of sulfur cathodes greatly influence the corresponding energy density, disclosing compatible regulation among active materials, tailored hosts, and elaborate cathodes is of great significance. This review summarizes the recent progress of sulfur cathodes classified by sulfur encapsulation, host architecture, and cathode configuration, aiming to illustrate their synergetic contribution to the improved electrochemical performance of Li-S batteries. The emphasis is centered on the integrated design principles with a focus on intrinsic mechanisms underlying their specific functions, providing a useful guideline for the future design of high energy density and long-term cycling Li-S batteries. (DOI: https://doi.org/10.1002/sus2.42)

Designing principles of advanced sulfur cathodes toward practical lithium‐sulfur batteries

AbstractAs one of the most promising candidates for next‐generation energy storage systems, lithium‐sulfur (Li‐S) batteries have gained wide attention owing to their ultrahigh theoretical energy density and low cost. Nevertheless, their road to commercial application is still full of thorns due to the inherent sluggish redox kinetics and severe polysulfides shuttle. Incorporating sulfur cathodes with adsorbents/catalysts has been proposed to be an effective strategy to address the foregoing challenges, whereas the complexity of sulfur cathodes resulting from the intricate design parameters greatly influences the corresponding energy density, which has been frequently ignored. In this review, the recent progress in design strategies of advanced sulfur cathodes is summarized and the significance of compatible regulation among sulfur active materials, tailored hosts, and elaborate cathode configuration is clarified, aiming to bridge the gap between fundamental research and practical application of Li‐S batteries. The representative strategies classified by sulfur encapsulation, host architecture, and cathode configuration are first highlighted to illustrate their synergetic contribution to the electrochemical performance improvement. Feasible integration principles are also proposed to guide the practical design of advanced sulfur cathodes. Finally, prospects and future directions are provided to realize high energy density and long‐life Li‐S batteries.

Sucrose Derived Hierarchical Porous Carbon as Sulfur Encapsulation Host for Durable Cycled Lithium-Sulfur Batteries

Sucrose Derived Hierarchical Porous Carbon as Sulfur Encapsulation Host for Durable Cycled Lithium-Sulfur Batteries