Sulfur Host For Lithium-sulfur Batteries Research Articles

Graphene-like porous carbon sheet/carbon nanotube composite as sulfur host for lithium-sulfur batteries

Graphene-like porous carbon sheet/carbon nanotube composite as sulfur host for lithium-sulfur batteries

Understanding the role played by Cu nanoparticles embedded in situ in a carbonaceous matrix as sulfur host for lithium-sulfur batteries

The lithium-sulfur (Li-S) battery is a promising alternative to Li-ion batteries as an energy storage system, owing to its higher capacity and specific energy values. To tackle its intrinsic problems, the element copper (Cu) is an attractive option given both its excellent conductivity and its ability to interact with highly reactive polysulfides. Here, we propose the use of a carbon/copper composite (90.5:9.5 wt ratio) obtained by thermal decomposition of a single precursor based on a Cu(II) oleate/oleic acid complex and eliminating the use of H2 as a reducing agent as commonly reported. Cu nanoparticles (mean particle size around 15 nm in diameter) which are highly dispersed on an amorphous carbon matrix derived from an organic framework, enhance both the conductivity and the ability for the chemical adsorption of lithium polysulfides (LiPSs), and thus increasing the reaction efficiency. Poor cycling stability, less specific capacity, and diminished rate capability were observed when the Cu content was reduced to around 70 % through treatment with concentrated nitric acid. This confirms the electrocatalytic role of the metal.

Synergistic improvement of the sulfur redox reaction by MOF-driven dual-defect polyhedral Mn-doped Co1-xS embedded in an N-doped carbon composite host for practical lithium-sulfur batteries

In the quest for practical sulfur hosts for lithium-sulfur batteries, a novel approach has been delineated. By meticulously adjusting the Mn:Co (1:5/1:9/1:1) ratio and the sulfidation temperature, a series of nitrogen-doped carbon nanopolyhedron composites have been synthesized, denoted as 1:9 Mn-Co1-xS-NC@NC, 1:5 Mn-Co1-xS-NC@NC, 1:1 Mn-Co1-xS-NC@NC, and Co1-xS-NC@NC. These materials, inheriting the polyhedral shape and a novel cavity structure from their precursors, exhibit enhanced lithium polysulfide adsorption and catalytic activity due to the introduction of Mn heteroatoms and cobalt vacancies. The resultant S@1:9 Mn-Co1-xS-NC@NC cathode excels in electrochemical performance, delivering an initial discharge capacity of 999.37 mA h g−1 at 1 C, and sustaining 715.65 mA h g−1 over 100 cycles. Notably, at an elevated sulfur loading of 3.05 mg cm−2 (E/S, 14.5 uL g−1), the cathode retains an areal capacity of 3.24 cmmA h cm−2 (corresponding specific capacity of 1067.59 mA h g−1) after 61 cycles at 0.2 C. The synergistic effect of manganese dopants and cobalt vacancies confers superior adsorptive and catalytic properties, presenting a promising avenue for the development of sulfur host materials with tailored morphologies and defect-rich structures.

Nickle-doped covalent organic frameworks/carbon nanotubes composite for high-performance lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) are considered as one of the most promising next-generation energy storage systems. To mitigate the shuttle effect of lithium polysulfides (LiPSs) in LSBs, the rational design of sulfur hosts with high physical confinement and catalytic activity is critical to enhance the performance of LSBs. Here, we successfully prepare a nickle-doped covalent organic frameworks/carbon nanotubes composite (Ni/COFs/CNTs) as the sulfur host in LSBs. COFs can confine and immobilize sulfur species. Moreover, CNTs and Ni nanoparticles can provide fastelectrontransferpathways. Thus, Ni/COFs/CNTs composite can alleviate the shuttle effect during the cycling processes.The S/Ni/COFs/CNTs cathode displays a high initial reversible capacity of 1068.6 mAh g−1 and a high capacity retention (83.3 %) after 100 cycles at 0.1C. This work provides a useful strategy to the rational design of sulfur hosts for LSBs.

Dual-engineering of tungsten doping and carbon incorporation in vanadium carbide arrays to accelerate the polysulfide conversion for lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are promising candidates for next-generation electrochemical energy storage systems by virtue of the high energy density, low-cost, and ecofriendliness. Unfortunately, the sluggish sulfur conversion kinetics, notorious shuttle effect of lithium polysulfides (LiPSs) and severe volumetric variation during the lithiation/delithiation process result in insufficient sulfur utilization and fast capacity degradation. Herein, tungsten-doped vanadium carbide nanosheet arrays strongly coupled with a thin nitrogen-doped carbon layer directly grown on carbon cloth substrate (denoted as CC/W-VC@NC) have been conceptually designed as an advanced sulfur host to resolve the aforementioned problems. Specifically, the binder-free CC/W-VC@NC sulfur host not only strongly interacts with LiPSs, but also presents superior electrocatalytic activity for rapid LiPSs conversion. Additionally, the arrayed architecture provides sufficient space for sulfur loading and simultaneously accommodates its volumetric variation. Furthermore, theoretical calculations elucidate that tungsten doping can regulate the electronic structure, improve the electrical conductivity and strengthen the chemisorption toward LiPSs. Attributing to the multifarious advantages, Li-S batteries assembled with CC/W-VC@NC/S cathode exhibit a high initial discharge capacity of 1305.9 mAh/g at 0.1 C, as well as superior rate capability (709.8 mAh/g at 5 C) and good long-term durability (capacity decay rate of only 0.063 % per cycle over 500 cycles at 1 C). This study presents an effective approach to construct transition metal carbides as high-performance sulfur hosts for Li-S batteries.

Single-atom decorated hollow mesoporous carbon spheres composited with free-standing carbon cloth supported cobalt sulfide nanowire arrays as high-performance sulfur host for lithium-sulfur batteries

BackgroundLithium-sulfur batteries (LSBs) are a promising next generation electrochemical energy storage device. Its commercialization however is hindered by several technical challenges, particularly shuttling of polysulfides. MethodsA composite sulfur host, coupled with a porous current collector, was developed to mitigate the shuttling problem. Iron single atom (SAFe) decorated hollow mesoporous carbon spheres (HMCS), composited with cobalt sulfide nanowire arrays supported on free-standing carbon cloth (S-Co@CC), were fabricated as a high-performance sulfur host for LSBs. The sulfur host combines the high electrical conductivity and physical confinement capability of HMCS, the excellent polysulfides chemisorption capability of cobalt sulfide nanowire arrays, and the high catalytic efficiency of iron single atoms toward polysulfide conversion reactions, to achieve a high-performance LSB. Significant findingsThe S-Co@CC/SAFe-HMCS based LSB exhibited a high initial specific capacity of 1430 mAh g−1 at 0.1 C. For cycling stability, a specific capacity of 578 mAh g−1 was maintained after a 600-cycle operation at 1 C, achieving an ultralow average capacity decay rate of 0.029 % per cycle. The design of composite sulfur hosts, combining all functional components in one, proves to be an effective strategy to advance the development of high-performance LSBs.

Synthesis of Nixp/C Nanofibers As Interlayer and Sulfur Host for Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSB) have a high theoretical capacity (1675 mAh g − 1) and energy density (2600 Wh kg−1), making them one of the most promising energy storage systems. 1 However, it has some limitations, such as “shuttle effect” of polysulfides and high volume expansion, causing poor cycle performance of the battery.The transition metal phosphides with carbon materials as sulfur host for LSB have attracted extensive scientific focus due to the large surface area and strong chemisorption ability. Moreover, high electrical conductivity of carbon-based material and the chemical adsorption effect of Ni-P phase can reduce the “shuttle effect”, and improve the cyclability of the material. 2,3 In this work, nickel phosphide carbon composite (NixP/C) nanofibers were synthesized using a water-soluble carbon source polyvinylpyrrolidone (PVP) and cost-effective electrospinning method. The impact of humidity on the physical and electrochemical characteristics of the electrospun NixP/C nanofibers was studied, utilizing them as interlayer and sulfur host material for LSB.The NixP/C nanofibers were synthesized using an electrospinning machine from PVP, nickel nitrate hexahydrate, and phosphoric acid as precursors. The nanofibers were electrospun at 18 kV voltage and 0.8 mL h–1 flow rate. The electrospinning humidity (RH) varied between 19-35%. Obtained nanofibers were dried at 110 ºC for 11 h. Finally, prepared fibers were annealed at 700 ºC for 1 h with a heating rate of 5 ºC min-1 in the N2 + H2 (4%) atmosphere.The crystalline phases of the final products were observed using X-Ray diffraction (XRD, Miniflex, Rigaku). The microstructure was studied by transmission electron microscopy (TEM, JEM-1400 Plus, JEOL). According to the results shown in Figure 1, Ni2P with a hexagonal structure and the space group of P62m, and Ni12P5 with a tetragonal structure, space group of 87:I4/m were formed. Nanoparticles of NixP are uniformly distributed within the carbon fiber matrix (inset).The NixP/C freestanding mats were embedded as a sulfur host or interlayer for LSB in CR2032 coin-type cells. 1 M Li2S6 catholyte solution and 1 M LiTFSI in 1,3- dioxolane (DOL)/1,2 dimethoxyethane (DME) (v/v, 1:1) with 2 wt% of LiNO3 were used as a source of sulfur and electrolyte, respectively. Further details and obtained results will be presented at the conference. Acknowledgements This research was funded by the projects AP13068219 “Development of multifunctional free-standing carbon composite nanofiber mats”, and AP19675260 “Development of nanofibrous electrode materials for next-generation lithium-ion batteries” from the Ministry of Education and Science of the Republic of Kazakhstan.

Single Atom Catalyst Anchored on Nitrogen-Doped Porous Carbon As an Effective Sulfur Host for Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) are considered highly promising for next-generation energy storage due to their high theoretical specific capacity and energy density. However, challenges such as the insulating nature of sulfur cathodes, the detrimental shuttle effect of lithium polysulfides (LiPSs), and sluggish conversion kinetics of LiPSs during charge/discharge cycles impede their commercial viability. In this study, we employed a facile ‘dissolution-carbonization’ approach to synthesize nitrogen-coordinated monometallic atomic catalysts anchored on mesoporous carbon to promote surface-mediated reactions of LiPSs. The hierarchical porous carbon support physically confines the sulfur species, while the introduction of single atoms efficiently captures polysulfide intermediates and facilitates their redox conversion kinetics with a lower activation energy barrier. The synergistic effect of the single atom and nitrogen-rich porous carbon (NC) significantly enhances reaction kinetics and sulfur species utilization. Consequently, LSBs incorporating single-atom catalysts (SACs) demonstrate remarkable performance metrics, including high-capacity retention (824.2 mAh g−1), superior Coulombic efficiency (>98.5%), low-capacity decay rate (0.042% per cycle) after 500 cycles at 1 C, and excellent rate capability (776 mA h g–1 at 3 C). This work presents an effective strategy that combines the functions of a nanoporous material host and SACs for lithium-sulfur batteries.

Hollow CoP-FeP cubes decorating carbon nanotubes heterostructural electrocatalyst for enhancing the bidirectional conversion of polysulfides in advanced lithium-sulfur batteries

The sluggish redox reaction kinetics and “shuttle effect” of lithium polysulfides (LPSs) impede the advancement of high-performance lithium-sulfur batteries (LSBs). Transition metal phosphides exhibit distinctive polarity, metallic properties, and tunable electron configuration, thereby demonstrating enhanced adsorption and electrocatalytic capabilities towards LPSs. Consequently, they are regarded as exceptional sulfur hosts for LSBs. Moreover, the introduction of a heterogeneous structure can enhance reaction kinetics and expedite the transport of electrons/ions. In this study, a composite of hollow CoP-FeP cubes with heterostructure modified carbon nanotube (CoFeP-CNTs) was fabricated and utilized as sulfur host in advanced LSBs. The presence of carbon nanotubes (CNTs) facilitates enhanced electron and Li+ transport. Meanwhile, the active sites within the heterogeneous interface of CoP-FeP suppress the “shuttle effect” and enhance the conversion kinetics of LPSs. Therefore, the CoFeP-CNTs/S electrode exhibited exceptional cycling stability and demonstrated a capacity attenuation of merely 0.051 % per cycle over 600 cycles at 1C. This study presents a highly effective tactic for synthesizing dual-acting transition metal phosphides with heterostructure, which will play a pivotal role in advancing the development of efficient LSBs.

Marine waste derived carbon materials for use as sulfur hosts for Lithium-Sulfur batteries

Lithium–sulfur batteries are a promising alternative to lithium-ion batteries as they can potentially offer significantly increased capacities and energy densities. The ever-increasing global battery market demonstrates that there will be an ongoing demand for cost effective battery electrode materials. Materials derived from waste products can simultaneously address two of the greatest challenges of today, i.e., waste management and the requirement to develop sustainable materials. In this study, we detail the carbonisation of gelatin from blue shark and chitin from prawns, both of which are currently considered as waste biproducts of the seafood industry. The chemical and physical properties of the resulting carbons are compared through a correlation of results from structural characterisation techniques, including electron imaging, X-ray diffraction, Raman spectroscopy and nitrogen gas adsorption. We investigated the application of the resulting carbons as sulfur-hosting electrode materials for use in lithium–sulfur batteries. Through comprehensive electrochemical characterisation, we demonstrate that value added porous carbons, derived from marine waste are promising electrode materials for lithium–sulfur batteries. Both samples demonstrated impressive capacity retention when galvanostatically cycled at a rate of C/5 for 500 cycles. This study highlights the importance of looking towards waste products as sustainable feeds for battery material production.

Hollow Defect-Rich Nanofibers as Sulfur Hosts for Lithium-Sulfur Batteries.

The slow redox kinetics of lithium-sulfur batteries severely limit their application, and sulfur utilization can be effectively enhanced by designing different cathode sulfur host materials. Herein, we report the hollow porous nanofiber LaNi0.6Co0.4O3 as a bidirectional host material for lithium-sulfur batteries. After Co is substituted into LaNiO3, oxygen vacancies are generated to enhance the material conductivity and enrich the active sites of the material, and the electrochemical reaction rate can be further accelerated by the synergistic catalytic ability of Ni and Co elements in the B-site of the active site of LaNi0.6Co0.4O3. As illustrated by the kinetic test results, LaNi0.6Co0.4O3 effectively accelerated the interconversion of lithium polysulfides, and the nucleation of Li2S and the dissolution rate of Li2S were significantly enhanced, indicating that LaNi0.6Co0.4O3 accelerated the redox kinetics of the lithium-sulfur battery during the charging and discharging process. In the electrochemical performance test, the initial discharge specific capacity of S/LaNi0.6Co0.4O3 was 1140.4 mAh g-1 at 0.1 C, and it was able to release a discharge specific capacity of 584.2 mAh g-1 at a rate of 5 C. It also showed excellent cycling ability in the long cycle test, with a single-cycle capacity degradation rate of only 0.08%. Even under the harsh conditions of high loaded sulfur and low electrolyte dosage, S/LaNi0.6Co0.4O3 still delivers excellent specific capacity and excellent cycling capability. Therefore, this study provides an idea for the future development of bidirectional high-activity electrocatalysts for lithium-sulfur batteries.

Triple Effect of "Conductivity-Adsorption-Catalysis" Enables MXene@FeCoNiP to be Sulfur Hosts for Lithium-Sulfur Batteries.

The weak chemical immobilization ability and poor catalytic effect of MXene inhibit its application in lithium-sulfur (Li-S) batteries. Herein, a novel MXene@FeCoNiP composite is rationally developed and utilized as a sulfur host for Li-S batteries. In this well-designed MXene-based nanostructure, the introduction of FeCoNiP in the interlayer of MXene nanosheets can not only effectively inhibit the restacking of MXene nanosheets but also act as an accelerator for the adsorption and catalysis of polysulfides to restrain the shuttling effect and facilitate the transformation of polysulfides. The existence of two-dimensional MXene nanosheets provides more active sites and improves the conductivity, which is beneficial for accelerating the reaction kinetics. Thus, the as-prepared MXene@FeCoNiP composites achieve an outstanding performance for Li-S batteries. This work provides an opportunity to construct an ideal sulfur host with the triple effect of "conductivity-adsorption-catalysis".

Preparation and application of NiS2/NiSe2 heterostructure as a sulfur host in lithium-sulfur batteries

The introduction of heterostructure in the cathode material of Li-S battery is an effective method to improve the redox reaction kinetics and suppress the shuttle effect of polysulfide. A metal sulfide/metal selenide (NiS2/NiSe2) heterostructure with hollow tetrahedral structure is prepared as a sulfur host of lithium-sulfur batteries. The prepared NiS2/NiSe2 heterostructure exhibits efficient charge transfer at the heterojunction interface, thereby enhancing catalytic activity for redox reactions of polysulfides and facilitating their rapid conversion. Moreover, the unique hollow tetrahedral structure, along with abundant surface pores, enables high sulfur loading capacity, providing abundant electrochemical reaction sites to enhance sulfur utilization efficiency. The results demonstrate that the NiS2/NiSe2 heterostructure material exhibits a remarkable initial capacity of 1338.9 mAh/g at 0.2 C, along with exceptional cycling stability (maintaining a capacity of 517.6 mAh/g after 200 cycles at 0.2 C, with only a negligible decay rate of 0.3% per cycle, retaining a capacity of 462.6 mAh/g after 500 cycles at 1 C, with an insignificant decay rate of merely 0.12% per cycle). The facile preparation of this NiS2/NiSe2 heterostructure not only enables the realization of lithium-sulfur batteries with exceptional capacity, but also opens up broader avenues for exploring high-performance heterogeneous materials.

La-doped Porous Fe2O3 Nanorods as Advanced Anodes for Lithium/Sodium Ion Batteries and Sulfur Host for Li-Sulfur Batteries.

Transition metal oxides are investigated as electrochemically active anodes for several years due to the merits of high specific capacity, low cost, abundant resources and controllable synthesis. But the poor cycle performances have hindered their further wide application. Herein, porous La-doped FeOOH nanorods have been synthesized through a facile hydrothermal method, which could be transformed into porous La-doped Fe2O3 (Fe2O3-La) via a simple heating process. Compared with the undoped Fe2O3, the Fe2O3-La showed larger surface area, higher specific capacities and more stable cycle performances for lithium/sodium ion batteries. In addition, as an advanced sulfur host for lithium-sulfur batteries, the Fe2O3-La also displayed much more excellent cycle and rate performances than the undoped Fe2O3. The superior electrochemical performances of the Fe2O3-La may could be attributed to the doping of La, which could induce more porous morphology and offer more reactive sites. The positive effects of La-doping for electrochemical performances of porous Fe2O3 nanorods provide novel insights for further applications of rare earth metal doping.

Arginine modification of hybrid cobalt/nitrogen Ti3C2Tx MXene and its application as a sulfur host for lithium-sulfur batteries

The shuttling effect of lithium polysulfides (LiPSs) is one of the challenges facing the commercialization, which leads to a significant capacity degradation. This paper proposes a novel method to promote polysulfide transformation by employing arginine to regulate the layer spacing of cobalt-nitrogen doped Ti3C2Tx MXene (Co-N@Ti3C2Tx-Arg). The results revealed that arginine effectively extended the interlayer spacing and promoted the homogeneous dispersion of Co and N atoms, thus endowing the sulfur host with a high catalytic activity during the charging and discharging processes. The extended interlayer spacing increased the specific surface area and captured sufficient LiPSs for subsequent catalytic conversions, while the Co and N doping on the surface of Ti3C2Tx significantly promoted the rapid conversion of the LiPSs to Li2S. Therefore, the S cathode coated with Co-N@Ti3C2Tx-Arg exhibited an excellent cycling stability with a low-capacity fading rate of 0.083% over 200 cycles in addition to a high reversible capacity of 1,365.4 mAh g-1 at 0.1 C.

Hollow and Silver-Cored Carbon Nanospheres as Effective Sulfur Hosts for Lithium-Sulfur Batteries

Lithium sulfur (Li–S) batteries are considered to be one of the most promising “beyond lithium-ion” energy storage technologies and the development of alternative battery chemistries is required to alleviate our reliance on the burning of fossil fuels 1. The high theoretical specific capacity of sulfur (1672mAh g-1) leads to a theoretical specific energy of ~2510 Wh kg-1, which is significantly greater than the state-of-the-art lithium-ion batteries 2. Further to this, sulfur is environmentally benign, low cost, and Li–S batteries do not rely on cobalt, or manganese 3, which are expensive, toxic, and have known ethical implications associated with their extraction and refining 4.While Li–S batteries boast many theoretical advantages, their practical application has been plagued with an array of limitations, mainly attributed to the poor electrical conductivity of sulfur, the significant volumetric expansions (80%) that can occur during cycling, and the soluble polysulfide intermediates 5. To tackle this, current research efforts have focused on using porous carbon materials (PCMs) to prepare sulfur/carbon composite cathodes 6,7. PCMs offer improved electrical conductivity, a large specific surface area, and pore diameters that are less than 1nm—which may confine the soluble polysulfides within the cathode matrix 8.In this study, the synthesis of hollow and silver-cored carbon nanospheres (HCNS, Ag-CNS) is detailed and their use as a multifunctional sulfur host for Li–S batteries is assessed. Ag-CNS are synthesised via a hydrothermal procedure from a simple saccharide solution coupled with a silver precursor. These Ag-CNS are further processed to prepare HCNS by etching the internal silver nanoparticle with an acid solution. The hydrothermal procedure described in this study offers a simplification to traditional HCNS synthesis methods which typically require the removal of templates, such as silica nanospheres, through etching with hazardous chemicals such as hydrofluoric acid.In this work, the structural and physical properties of HCNS and Ag-CNS are characterised using transmission electron microscopy, scanning electron microscopy, nitrogen gas adsorption, X-ray diffraction, Raman spectroscopy, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The electrochemical performance of these materials, when used as a sulfur host, is investigated through the preparation, and testing of half cells with lithium metal anodes. Electrochemical testes include cyclic voltammetry and galvanostatic cycling data at different C-rates.

Reduced graphene oxide wrapped ZnCo layered double hydroxides microsphere as efficient sulfur host in lithium-sulfur batteries

The practical application of lithium-sulfur (Li-S) batteries is impeded by the shuttling of the polysulfide and slow sulfur electrochemical reaction. In this study, a reduced graphene oxide (rGO) wrapped hollow ZnCo layered double hydroxides (ZnCo-LDH) microsphere is fabricated as sulfur host material. The rGO nanosheets offer efficient charge transportation pathways. Meanwhile, the porous rGO and hollow ZnCo-LDH provide sufficient space for sulfur storage and mitigates the volume variation during battery charging and discharging. In addition, ZnCo-LDH exhibits excellent chemical adsorption capacity for polysulfides, and promotes their electrochemical conversion reactions. Benefited from these advantages, the S/ZnCo-LDH@rGO cathode delivers a high rate performance of 796.5 mAh g−1 at 5.0 C, and excellent stability performance with a capacity decay of 0.036 % per cycle after 500 cycles at 1.0 C. This study shows that the porous microsphere design of rGO wrapped layered double hydroxides has excellent application prospects as efficient sulfur host for Li-S batteries.

A coral-like composite of CoP-modified polyaniline-derived carbon chain skeleton as an efficient sulfur host for lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) have attracted wide attention in the field of rechargeable batteries due to their high theoretical energy density. However, the severe “shuttle effect” of lithium polysulfides (LiPSs) and the slow conversion kinetics are key factors restricting the commercial application of LSBs. To address these issues, we designed and prepared a coral-like composite of CoP-modified polyaniline-derived carbon chain skeleton (CoP/C) as the sulfur host for LSBs. The carbon chains can provide multidirectional channels for the transport of Li+ and electron; and the uniformly scattered CoP can adsorb the LiPSs through chemical adsorption and simultaneously promote their conversion, thus the “shuttle effect” can be effectively alleviated. Meanwhile, the effect of the amount of aniline monomer on the electrochemical performance of sulfur cathode were studied. After sulfur loading, the CoP/C-300/S (with aniline monomer addition of 300 μL) exhibits the best electrochemical performance. At 1 C, after 500 cycles, it still maintains a reversible specific capacity of 478 mA h g−1, with a decay rate of 0.074% per cycle, indicating its excellent cycling stability. This work provides a new approach for the application of CoP material in advanced LSBs.

Deciphering the Influence of Anionic Electrons of Surface-Functionalized Two-Dimensional Electrides in Lithium-Sulfur Batteries.

Using transition metal compounds as sulfur hosts is regarded as a promising approach to suppress the polysulfide shuttle and accelerate redox kinetics for lithium-sulfur (Li-S) batteries. Herein, we report that a new kind of compound, electrides (exotic ionic crystalline materials in which electrons serve as anions), is efficient sulfur hosts for Li-S batteries for the first time. Based on the first-principles calculations, we found that two-dimensional (2D) electrides M2C (M = Sc, Y) exhibit unprecedentedly strong binding strength toward sulfur species and surface functionalization is necessary to passivate their activity. The 2D electrides modified with the F-functional group exhibit the best performance in terms of the adsorption energy and sulfur reduction process. A comparative study with a nonelectride reveals that the anionic electrons (AEs) of electrides aid in anchoring the soluble polysulfides. These results open an avenue for the application of electrides in Li-S batteries.

Sub-nanometer cobalt clusters embedded carbon networks to promote the kinetics of polysulfide conversion

The sluggish oxidation-reduction kinetics of sulfur and the shuttle effect of polysulfides are the bottlenecks restricting the practical application of lithium-sulfur batteries. In this study, subnanometer cobalt clusters were embedded into the cross-linked network of carbon sheets framework as high-efficiency sulfur host materials to promote the kinetics of polysulfides conversion for lithium-sulfur batteries. In such composite structure, the carbon network provides a rapid electron transfer pathway for interfacial electrochemical reaction. Co and N atoms can chemisorb polysulfides by forming Co-S and Li-N bonds with polysulfides, and catalyze the conversion of polysulfides. Such structure exhibits excellent rate performance and cycle stability during the cycle of lithium-sulfur battery. The capacity decay rate per cycle is only 0.061% for 500 cycles at 1 C, and the capacity retention rate is 69.4%. The composite structure developed in this work is a promising and high-efficiency sulfur host for lithium-sulfur batteries.