Electrochemically Active MoO3/TiN Sulfur Host Inducing Dynamically Reinforced Built-in Electric Field for Advanced Lithium-Sulfur Batteries.

Although various electrocatalysts have been developed to ameliorate the shuttle effect and sluggish Li-S conversion kinetics, their electrochemical inertness limits the sufficient performance improvement of lithium-sulfur batteries (LSBs). In this work, an electrochemically active MoO3/TiN-based heterostructure (MOTN) is designed as an efficient sulfur host that can improve the overall electrochemical properties of LSBs via prominent lithiation behaviors. By accommodating Li ions into MoO3 nanoplates, the MOTN host can contribute its own capacity. Furthermore, the Li intercalation process dynamically affects the electronic interaction between MoO3 and TiN and thus significantly reinforces the built-in electric field, which further improves the comprehensive electrocatalytic abilities of the MOTN host. Because of these merits, the MOTN host-based sulfur cathode delivers an exceptional specific capacity of 2520 mA h g-1 at 0.1 C. Furthermore, the cathode exhibits superior rate capability (564 mA h g-1 at 5 C), excellent cycling stability (capacity fade rate of 0.034% per cycle for 1200 cycles at 2 C), and satisfactory areal capacity (6.6 mA h cm-2) under a high sulfur loading of 8.3 mg cm-2. This study provides a novel strategy to develop electrochemically active heterostructured electrocatalysts and rationally manipulate the built-in electric field for achieving high-performance LSBs.

A Review of Electrospun Carbon-based Nanofibers Materials Used in Lithium-Sulfur Batteries.

Commercial lithium-ion batteries are gradually approaching their theoretical values (200-250 Wh kg-1), which cannot meet the fast-growing energy storage demands. Lithium-sulfur (Li-S) batteries are anticipated to supersede lithium-ion batteries as the next-generation energy storage system owing to their high theoretical specific capacity (1675 mAh g-1) and energy density (2600 Wh kg-1). Nonetheless, Li-S batteries encounter several challenges, including the inadequate conductivity of sulfur and lithium sulfide, sulfur's volume expansion, and the shuttle effect of lithium polysulfides, all of which significantly impact the practical utilization of Li-S batteries. Electrospun carbon-based nanofibers can simultaneously resolve these issues with their economical preparation, distinctive nanostructure, and exceptional flexibility. This review presents the most recent research findings on electrospun carbon-based nanofibers materials serving as sulfur hosts and interlayer components in Li-S batteries. We analyzed the impact of the material's structural design on the performance of Li-S batteries and the relative underlying mechanism. Finally, the current challenges and issues faced by carbon-based nanofibers composites in the application of Li-S batteries are summarized, and the future development trajectory are outlined.

Construction of N-doped carbon encapsulated CoP hollow nanofibers as multifunctional electrode materials for potassium-ion and lithium-sulfur batteries.

Herein, a composite of N-doped carbon coated phosphating cobalt hollow nanofibers (N/C@CoP-HNFs) was synthesized by electrospinning, phosphating, and carbon coating processes. When employed as multifunctional electrode materials for potassium-ion batteries (PIBs) and lithium-sulfur (Li-S) batteries, the N/C@CoP-HNFs demonstrated notable electrochemical properties. Specifically, it delivered an initial specific capacity of 420.4 mA h g-1 at a current density of 100 mA g-1, with a sustained capacity of 190.8 mA h g-1 after 200 cycles in PIBs, and a specific capacity of 1448 mA h g-1 at a current density of 0.5C in Li-S batteries, which is considered relatively high for these types of battery technology. This good performance may due to the combination of the carbon nitrogen layer and cobalt phosphide bilayer hollow tube structure, which is conducive to telescoping the diffusion length of ions and electrons and buffer volume variation, and effectively inhibits the shuttle effect. Density functional theory (DFT) calculations were also used to explore the energy storage mechanism of the material. The possible adsorption sites and corresponding adsorption energy of K+ were analyzed, and the advantages of the material were explored by calculating the diffusion barrier and state density. The theoretical simulations further validated the strong adsorption capability of CoP for polysulfides. This work is expected to provide new ideas for new energy storage materials.

Precisely Designed Ultra-Small CoP Nanoparticles-Decorated Hollow Carbon Nanospheres as Highly Efficient Host in Lithium-Sulfur Batteries.

Designing porous carbon materials with metal phosphides as host materials holds promise for enhancing the cyclability and durability of lithium-sulfur (Li-S) batteries by mitigating sulfur poisoning and exhibiting high electrocatalytic activity. Nevertheless, it is urgent to precisely control the size of metal phosphides to further optimize the polysulfide conversion reaction kinetics of Li-S batteries. Herein, a subtlety regulation strategy was proposed to obtain ultra-small CoP nanoparticles-decorated hollow carbon nanospheres (CoP@C) by using spherical polyelectrolyte brush (SPB) as the template with stabilizing assistance from polydopamine coating, which also works as carbon source. Leveraging the electrostatic interaction between SPB and Co2+, ultra-small Co particles with sizes measuring 5.5±2.6 nm were endowed after calcination. Subsequently, through a gas-solid phosphating process, these Co particles were converted into CoP nanoparticles with significantly finer sizes (7.1±3.1 nm) compared to state-of-the-art approaches. By uniformly distributing the electrocatalyst nanoparticles on hollow carbon nanospheres, CoP@C facilitated the acceleration of Li-ion diffusion and enhanced the conversion reaction kinetics of polysulfides through adsorption-diffusion synergy. As a result, Li-S batteries utilizing the CoP@C/S cathode demonstrated an initial specific discharge capacity of 850.0 mAh g-1 at 1.0 C, with a low-capacity decay rate of 0.03 % per cycle.

Fabrication of Fe/KB Composite as Sulfur Host for Li-S Battery.

Lithium sulfur battery is a novel kind of secondary battery which has high energy density, however its application is greatly affected by the shuttle effect of polysulfides generated in the redox reaction of cathode electrode. Metal active sites are supposed as effective catalysts which can absorb and accelerate the conversion efficiency of lithium polysulfides, thus the shuttle effect will be alleviated. In this work, we conducted a simple way to prepare a metal Fe doped ketjen black to serve as the sulfur host of lithium sulfur battery. Ketjen black has a large specific surface area and rich porous structure, while Fe nanodot is an excellent catalyst for lithium polysulfides. Because of these advantages, the Fe/KB host can effectively confine a large amount of active material and accelerate its, therefore the Fe/KB-S cathode electrode show an excellent electrochemical performance.

Boron dopant- and nitrogen defect-decorated C3N5 porous nanostructure as an efficient sulfur host for lithium-sulfur batteries.

Active site implantation and morphology manipulation are efficient protocols for boosting the electrochemical performance of carbon nitrides. As a promising sulfur host for lithium-sulfur batteries (LSBs), in this study, C3N5 porous nanostructure incorporated with both boron (B) atoms and nitrogen (N) defects was constructed (denoted as ND-B-C3N5) using a two-step strategy, i.e., pyrolysis of the mixture of 3-amino-1,2, 4-triazole and boric acid to obtain B-doped C3N5 porous nanostructure and then KOH etching under hydrothermal condition to generate N defects. The doped B atoms in the C3N5 porous nanostructure are in the form of B-N bonds and grafted B-O bonds. N defects are primarily created at the CN-C positions of the triazine unit, leaving behind some N vacancies and cyano groups. Benefiting from the involvement of B dopants and N defects, the optimized ND-B-C3N5-12 sample exhibits ameliorative conductivity, mass transport, lithium polysulfides (LiPSs) adsorption ability, diffusion of Li+ ions, Li2S deposition capacity, sulfur redox polarization, and a reversible solid-solid sulfur redox process. Consequently, the ND-B-C3N5-12/S cathode delivers accelerated redox performance of polysulfides for LSBs, revealing capacities of 1091 ± 44 and 753 ± 20 mAh/g at 0.2C for the initial and 300th cycles, respectively. The ND-B-C3N5-12/S cathode is also endowed with desired sulfur redox activity and stability at 2C for 1000 cycles, holding an initial discharging capacity of 788 ± 24 mAh/g and a low decay rate of 0.05 % per cycle.

Nitrogen-Doped CoP with optimized d-Band center as bidirectional electrocatalyst for high areal capacity of Li-S battery.

Lithium polysulfide (LiPSs) shuttle effect and difficulties with Li2S oxidation are hinder the marketization of lithium-sulfur batteries. We suggest using a bidirectional catalyst in the sulfur host to solve these problems. We produced a nitrogen-doped cobalt phosphide (N-CoP@NC) as a sulfur carrier in this work. The introduction of nitrogen into cobalt phosphide enhances the electron transmission speed and forms shorter Co-N bonds. As a result, new defect energy levels are introduced, leading to an increase in the charge number of Co central atoms, which abate the Li-S and SS bonds in Li2S and Li2S4, thereby promoting the oxidation of Li2S during charging, as well as the alteration process of LiPSs during charge and discharge. Additionally, the crystal flaws that result in increased Co-S bond formation help to boost polysulfides' adsorption ability. The Li-S batteries shows outstanding cyclability when paired with this electrocatalyst, demonstrating a minimal capacity degradation rate of only 0.07 % per cycle over 500 cycles at a rate of 0.5C. As a result, incorporating anion doping in the host emerges as a promising method for crafting materials tailored for Li-S batteries.

Dependence of Interlayer or Sulfur Host on Hollow Framework of Lithium-Sulfur Battery.

Lithium-sulfur batteries are recognized as the next generation of high-specific energy secondary batteries owing to their satisfactory theoretical specific capacity and energy density. However, their commercial application is greatly limited by a series of problems, including disordered migration behavior, sluggish redox kinetics, and the serious shuttle effect of lithium polysulfides. One of the most efficient approaches to physically limit the shuttle effect is the rational design of a hollow framework as sulfur host. However, the influence of the hollow structure on the interlayers has not been clearly reported. In this study, the Mo2C/C catalysts with hollow(H-Mo2C/C) and solid(S-Mo2C/C) frameworks are rationally designed to explore the dependence of the hollow structure on the interlayer or sulfur host. In contrast to the physical limitations of the hollow framework as host, the hollow structure of the interlayer inhibited lithium-ion diffusion, resulting in poor electrochemical properties at high current densities. Based on the superiority of the various frameworks, the H-Mo2C/C@S | S-Mo2C/C@PP | Li cells are assembled and displayed excellent electrochemical performance. This work re-examines the design requirements and principles of catalyst frameworks in different battery units.

Fabrication of NiFe-LDHs Modified Carbon Nanotubes as the High-Performance Sulfur Host for Lithium-Sulfur Batteries.

Lithium-sulfur batteries offer the potential for significantly higher energy density and cost-effectiveness. However, their progress has been hindered by challenges such as the "shuttle effect" caused by lithium polysulfides and the volume expansion of sulfur during the lithiation process. These limitations have impeded the widespread adoption of lithium-sulfur batteries in various applications. It is urgent to explore the high-performance sulfur host to improve the electrochemical performance of the sulfur electrode. Herein, bimetallic NiFe hydroxide (NiFe-LDH)-modified carbon nanotubes (CNTs) are prepared as the sulfur host materials (NiFe-CNT@S) for loading of sulfur. On the one hand, the crosslinked CNTs can increase the electron conductivity of the sulfur host as well as disperse NiFe-LDHs nanosheets. On the other hand, NiFe-LDHs command the capability of strongly adsorbing lithium polysulfides and also accelerate their conversion, which effectively suppresses the shuttle effect problem in lithium polysulfides. Hence, the electrochemical properties of NiFe-CNT@S exhibit significant enhancements when compared with those of the sulfur-supported pure NiFe-LDHs (NiFe-LDH@S). The initial capacity of NiFe-CNT@S is reported to be 1010 mAh g-1. This value represents the maximum amount of charge that the material can store per gram when it is first synthesized or used in a battery. After undergoing 500 cycles at a rate of 2 C (1 C = 1675 mA g-1), the NiFe-CNT@S composite demonstrates a sustained capacity of 876 mAh g-1. Capacity retention is a measure of how well a battery or electrode material can maintain its capacity over repeated charge-discharge cycles, and a higher retention percentage indicates better durability and stability of the material.

Constructing the Interconnected Charge Transfer Pathways in Sulfur Composite Cathode for All-Solid-State Lithium-Sulfur Batteries.

All-solid-state lithium-sulfur batteries (ASSLSBs) have advantageous features, such as high energy, low costs, enhanced safety, and no polysulfide dissolution. However, the use of sulfur as an active material in all-solid-state batteries is difficult because of its ionic and electrical insulating properties. Herein, we introduce a flower-shaped composite material consisting of MoS2 nanoparticles and sulfur, designed to establish interconnected ionic and electrical conduction pathways at the cathode. As a host material, MoS2 nanoparticles with a large specific surface area can coconduct Li ions and electrons, possessing the potential for effectively utilizing sulfur. However, MoS2 nanoparticles are prone to physical-electrochemical isolation by being surrounded by sulfur due to their crumpling property in the process of mixing and impregnation with sulfur. This problem is addressed by mildly milling the MoS2 nanoparticles and sulfur, after which melt diffusion is applied to generate uniform MoS2/sulfur composite materials to establish an interconnected conducting pathway within the composite. A sulfide solid electrolyte (Li6PS5Cl)-based ASSLSB incorporating the proposed MoS2/sulfur composite demonstrates a stable operation over 1000 cycles with a Coulombic efficiency of nearly 100%. This study emphasizes the significance of the structural design of the sulfur composite material on top of the intrinsic properties of the material for high-performance ASSLSBs.

Single-Atomic Dispersion of Fe and Co Supported on Reduced Graphene Oxide for High-Performance Lithium-Sulfur Batteries.

High theoretical energy density and low cost make lithium-sulfur (LSB) batteries a promising system for next-generation energy storage. LSB performance largely depends on efficient reversible conversion of elemental sulfur to Li2S. Here, well-designed sulfur host materials including Fe or Co single atoms embedded on N-doped reduced graphene oxide (MNC/G with M = Fe or Co) are proposed to tackle the LSB challenges and enhance the electrochemical performance. Using a combination of Mössbauer spectroscopy and high-resolution scanning electron microscopy, the atomic dispersion of Co and Fe was revealed up to relatively high mass loadings. After optimization of the electrolyte/sulfur (E/S) ratio, FeNC/G shows the most promising cycle performance combining a constant high discharge capacity at low E/S values with the lowest polarization. In particular, the material FeNC/G@S with a high sulfur loading (9.4 mg cm-2) delivers a high area capacity of 7.7 mAh cm-2 under lean electrolyte conditions (6 mL g-1).

Two-birds with one stone: Improving both cathode and anode electrochemical performances via two-dimensional Te-CoTe2/rGO ultrathin nanosheets as sulfur hosts in lithium-sulfur batteries.

A Te-doped CoTe2 film could be grown in situ on reduced graphene oxide (rGO) to develop a Te-CoTe2/rGO composite with an ultrathin layered structure, which has multiple protective effects on both the sulfur positive electrode and lithium negative electrode in lithium sulfur (Li-S) batteries. The Te-CoTe2/rGO composite as a sulfur host not only shows a strong adsorbing ability for lithium polysulfides (LiPSs) but can also accelerate the conversion reaction of active material sulfur during the charging/discharging process. More importantly, this host can turn the shuttle effect from an unfavorable factor to a favorable factor, which could improve the electrochemical performance of the lithium anode with uniform lithium plating/stripping resulting from the intermediate polytellurosulfide species (Li2TexSy), which could be generated on the cathode surface via Te reacting with soluble Li2Sn (4 ≤ n ≤ 8). As a result, the S@Te-CoTe2/rGO cathode shows a discharge capacity of 970.0 mA h g-1 in the first cycle at 1 C and retains a high capacity of 545.5 mA h g-1 after 1000 cycles, corresponding to a low capacity decay rate of only 0.043% per cycle. In addition, in situ X-ray diffraction (XRD) and in situ Raman were used to explore the sulfur conversion process. This study not only demonstrates that a two-dimensional (2D) ultrathin Te-CoTe2/rGO composite is successfully developed with multiple effects on Li-S batteries but also opens a new pathway for designing unique sulfur hosts to promote the electrochemical performance of Li-S batteries.

Construction of Polypyrrole-Coated CoSe2 Composite Material for Lithium-Sulfur Battery.

Lithium-sulfur batteries with high theoretical energy density and cheap cost can meet people's need for efficient energy storage, and have become a focus of the research on lithium-ion batteries. However, owing to their poor conductivity and "shuttle effect", lithium-sulfur batteries are difficult to commercialize. In order to solve this problem, herein a polyhedral hollow structure of cobalt selenide (CoSe2) was synthesized by a simple one-step carbonization and selenization method using metal-organic bone MOFs (ZIF-67) as template and precursor. CoSe2 is coated with conductive polymer polypyrrole (PPy) to settle the matter of poor electroconductibility of the composite and limit the outflow of polysulfide compounds. The prepared CoSe2@PPy-S composite cathode shows reversible capacities of 341 mAh g-1 at 3 C, and good cycle stability with a small capacity attenuation rate of 0.072% per cycle. The structure of CoSe2 can have certain adsorption and conversion effects on polysulfide compounds, increase the conductivity after coating PPy, and further enhance the electrochemical property of lithium-sulfur cathode material.

Reducing Overpotential of Solid-State Sulfide Conversion in Potassium-Sulfur Batteries.

Improving kinetics of solid-state sulfide conversion in sulfur cathodes can enhance sulfur utilization of metal-sulfur batteries. However, fundamental understanding of the solid-state conversion remains to be achieved. Here, taking potassium-sulfur batteries as a model system, we for the first time report the reducing overpotential of solid-state sulfide conversion via the meta-stable S3 2- intermediates on transition metal single-atom sulfur hosts. The catalytic sulfur host containing Cu single atoms demonstrates high capacities of 1595 and 1226 mAh g-1 at current densities of 335 and 1675 mA g-1 , respectively, with stable Coulombic efficiency of ≈100 %. Combined spectroscopic characterizations and theoretical computations reveal that the relatively weak Cu-S bonding results in low overpotential of solid-state sulfide conversion and high sulfur utilization. The elucidation of solid-state sulfide conversion mechanism can direct the exploration of highly efficient metal-sulfur batteries.

Polyaniline-Coated Porous Vanadium Nitride Microrods for Enhanced Performance of a Lithium-Sulfur Battery.

To solve the slow kinetics of polysulfide conversion reaction in Li-S battery, many transition metal nitrides were developed for sulfur hosts. Herein, novel polyaniline-coated porous vanadium nitride (VN) microrods were synthesized via a calcination, washing and polyaniline-coating process, which served as sulfur host for Li-S battery exhibited high electrochemical performance. The porous VN microrods with high specific surface area provided enough interspace to overcome the volume change of the cathode. The outer layer of polyaniline as a conductive shell enhanced the cathode conductivity, effectively blocked the shuttle effect of polysulfides, thus improving the cycling capacity of Li-S battery. The cathode exhibited an initial capacity of 1007 mAh g-1 at 0.5 A g-1, and the reversible capacity remained at 735 mAh g-1 over 150 cycles.

Oxygen vacancy-mediated amorphous GeOx assisted polysulfide redox kinetics for room-temperature sodium-sulfur batteries.

The practical applications of room-temperature sodium-sulfur (RT Na-S) batteries have been greatly hindered by the natural sluggish reaction kinetics of sulfur and the shuttle effect of sodium polysulfide (NaPSs). Herein, oxygen vacancy (OV)-mediated amorphous GeOx/nitrogen doped carbon (donated as GeOx/NC) composites were well designed as sulfur hosts for RT Na-S batteries. Experimental and density functional theory studies show that the introduction of oxygen vacancies on GeOx/NC can effectively immobilize polysulfides and accelerate the redox kinetics of polysulfides. Meanwhile, the micro-and mesoporous framework, acting as a reactor for storing active S, is conducive to alleviating the expansion of S during the charging/discharging process. Consequently, the S@GeOx/NC cathode affords a reversible capacity of 1017 mA h g-1 at 0.1 A g-1 after 100 cycles, outstanding rate capability of 333 mA h g-1 at 10.0 A g-1 and long lifespan cyclability of 385 mAh g-1 at 1 A g-1 after 1200 cycles. This work furnishes a new way for the rational design of metal oxides with oxygen vacancies and boosts the application for RT Na-S batteries.

CuCo2S4 Nanoparticles Embedded in Carbon Nanotube Networks as Sulfur Hosts for High Performance Lithium-Sulfur Batteries.

Rational design of sulfur hosts for lithium-sulfur (Li-S) batteries is essential to address the shuttle effect and accelerate reaction kinetics. Herein, the composites of bimetallic sulfide CuCo2S4 loaded on carbon nanotubes (CNTs) are prepared by hydrothermal method. By regulating the loading of CuCo2S4 nanoparticles, it is found that when Cu2+ and CNT are prepared in a 10:1 ratio, the CuCo2S4 nanoparticles loaded on the CNT are relatively uniformly distributed, avoiding the occurrence of agglomeration, which improves the electrical conductivity and number of active sites. Through a series of electrochemical performance tests, the S/CuCo2S4-1/CNT presents a discharge specific capacity of 1021 mAh g-1 at 0.2 C after 100 cycles, showing good cycling stability. Even at 1 C, the S/CuCo2S4-1/CNT cathode delivers a discharge capacity of 627 mAh g-1 after 500 cycles. This study offers a promising strategy for the design of bimetallic sulfide-based sulfur hosts in Li-S batteries.

Zirconia-supported cobalt nanoparticles as high-performance sulfur cathode for lithium-sulfur batteries.

Lithium-sulfur (Li-S) battery is now a promising technology for energy storage. However, rapid capacity decay due to sulfur dissolution and shutting effect severely limit its commercial development. In this work, a NH2-UIO-66 metal organic framework-derived porous composite (Co-ZrO2@NC) consists of nitrogen-doped carbon (NC) and zirconium oxide (ZrO2) loaded with cobalt nanoparticles was prepared. The porous NC component not only increases the accommodation of sulfur in the cathode, but also benefits the charge transfer in sulfur electrochemistry. The Co and ZrO2would act as active centers to enhance the adsorption/conversion of lithium polysulfide and improve its electrochemical utilization. When used in sulfur cathode, the Co-ZrO2@NC electrode shows excellent electrochemical performance with an initial specific capacity of 1073 mAh g-1at a rate of 0.2 C and a reversible capacity of 1015 mAh g-1after 100 cycles, corresponding to a capacity retention of 94.6%. Furthermore, after 300 cycles at 1.0 C, corresponding to a capacity retention of 75.4%. Moreover, the cell also exhibits good rate performance (640 mAh g-1at 3.0 C). Even at high sulfur loading of 4.0 mg cm-2, the S/Co-ZrO2@NC cathode is able to deliver an areal specific capacity of 4.8 mAh cm-2.

Copper Zinc Sulfide (CuZnS) Quantum Dot-Decorated (NiCo)-S/Conductive Carbon Matrix as the Cathode for Li-S Batteries.

Sulfur composites consisting of electrochemical reactive catalysts/conductive materials are investigated for use in lithium-sulfur (Li-S) batteries (LSBs). In this paper, we report the synthesis, physicochemical and electrochemical properties of CuZnS quantum dots (CZSQDs) decorated with nickel-cobalt-sulfide ((NiCo)-S)) mixed with reduced graphene oxide (rGO)/oxidized carbon nanotube (oxdCNT) (rGO/oxdCNT) ((NiCo)-S@rGO/oxdCNT) composites. These composites are for the purpose of being the sulfur host cathode in Li-S batteries. The as-prepared composites showed a porous structure with the CZSQDs being uniformly found on the surface of the rGO/oxdCNT, which had a specific surface area of 26.54 m2/g. Electrochemical studies indicated that the (NiCo)-S@rGO/oxdCNT cells forming the cathode exhibited a maximum capacity of 1154.96 mAhg-1 with the initial discharge at 0.1 C. The smaller size of the CZSQDs (~10 nm) had a positive effect on the CZSQDs@(NiCo)-S@rGO/oxdCNT composites in that they had a higher initial discharge capacity of 1344.18 mAhg-1 at 0.1 C with the Coulombic efficiency being maintained at almost 97.62% during cycling. This latter property is approximately 1.16 times more compared to the absence of the Cu-Zn-S QD loading. This study shows that the CuZnS quantum dots decorated with a (NiCo)-S@rGO/oxdCNT supporting matrix-based sulfur cathode have the potential to improve the performance of future lithium-sulfur batteries.

Poly(ionic liquid) Nanovesicle-Templated Carbon Nanocapsules Functionalized with Uniform Iron Nitride Nanoparticles as Catalytic Sulfur Host for Li-S Batteries.

Poly(ionic liquid)s (PIL) are common precursors for heteroatom-doped carbon materials. Despite a relatively higher carbonization yield, the PIL-to-carbon conversion process faces challenges in preserving morphological and structural motifs on the nanoscale. Assisted by a thin polydopamine coating route and ion exchange, imidazolium-based PIL nanovesicles were successfully applied in morphology-maintaining carbonization to prepare carbon composite nanocapsules. Extending this strategy further to their composites, we demonstrate the synthesis of carbon composite nanocapsules functionalized with iron nitride nanoparticles of an ultrafine, uniform size of 3-5 nm (termed "FexN@C"). Due to its unique nanostructure, the sulfur-loaded FexN@C electrode was tested to efficiently mitigate the notorious shuttle effect of lithium polysulfides (LiPSs) in Li-S batteries. The cavity of the carbon nanocapsules was spotted to better the loading content of sulfur. The well-dispersed iron nitride nanoparticles effectively catalyze the conversion of LiPSs to Li2S, owing to their high electronic conductivity and strong binding power to LiPSs. Benefiting from this well-crafted composite nanostructure, the constructed FexN@C/S cathode demonstrated a fairly high discharge capacity of 1085 mAh g-1 at 0.5 C initially, and a remaining value of 930 mAh g-1 after 200 cycles. In addition, it exhibits an excellent rate capability with a high initial discharge capacity of 889.8 mAh g-1 at 2 C. This facile PIL-to-nanocarbon synthetic approach is applicable for the exquisite design of complex hybrid carbon nanostructures with potential use in electrochemical energy storage and conversion.