Polysulfide Conversion Research Articles

Unveiling the Role of Electric Double-Layer in Sulfur Catalysis for Batteries.

The metal-catalyzed sulfur reaction in lithium-sulfur (Li-S) batteries usually suffers from the strong binding of sulfur species to the catalyst surface, which destroys the electric double layer (EDL) region there. This causes rapid catalyst deactivation because it prevents the desorption of sulfur species and mass transport through the EDL is hindered. This work introduces a competitive adsorption factor (fsulfur) as a new indicator to quantify the competitive adsorption of sulfur species in the EDL and proposes an alloying method to change it by strengthening the p-d hybridization of alloying metals with electrolyte solvents. A cobalt-zinc alloy catalyst with a moderate fsulfur lowers the activation energy of the rate-limiting step of the conversion of lithium polysulfides to lithium sulfide, giving a platform capacity proportion that is 96% of the theoretical value and has a greatly improved anti-passivation ability, especially at high sulfur loadings and lean electrolyte conditions (a low E/S ratio of 5µL mgS -1). A pouch cell using this approach has a high energy density of up to 464Wh kg-1. Such a competitive adsorption indicator and alloying strategy offer a new guideline for catalyst design and a practical electrocatalysis solution for Li-S batteries.

Oxygen deficient Eu2O3-δ synchronizes the shielding and catalytic conversion of polysulfides toward high-performance lithium sulfur batteries

Oxygen deficient Eu2O3-δ synchronizes the shielding and catalytic conversion of polysulfides toward high-performance lithium sulfur batteries

An Electron-Coupled Co-ZrO2 Nanodot Heterojunction Electrocatalyst with Lewis Acid-Base Site Pairs Enables High Redox Reaction Kinetics of Li-S Batteries.

Using electrocatalysts is effective in solving the slow reaction kinetics of polysulfides in Li-S batteries, but designing stable electrocatalysts with an integrated adsorption-catalysis-desorption system is challenging. Here, we report a stable metal-semiconductor (Co-ZrO2) heterojunction electrocatalyst fabricated by assembling electron-coupled Co-ZrO2 nanodots into macroporous carbon nanofibers. The Co-ZrO2 contact causes interfacial electron enrichment and electron transfer from Co to ZrO2, which creates abundant Lewis-acid sites on Co that can adsorb polysulfides. Simultaneously, the enriched interfacial electrons can activate the S-S bond and boost the catalytic conversion of long-chain polysulfides, while the ZrO2 with Lewis-base sites facilitate the desorption of short-chain polysulfides from the electrocatalyst. Moreover, the nanodot heterojunctions show great chemical stability and high redox reaction kinetics of polysulfides. Li-S batteries show high discharge capacities of 954.5 mA h·g-1 at 0.5 C with a retention of 84.9% over 200 cycles, and 710.2 mA hg-1 at 1 C with a retention of 98.6% over 200 cycles. This study provides an effective strategy for developing active and durable electrocatalysts for Li-S batteries.

Oriented structural design of MXene electrodes for lithium sulfur catalysis

The lithium-sulfur reaction can contribute to the chemical electrical energy conversion capacity due to the multi-level ion/electron transfer process. However, the appearance of soluble intermediate products prevents efficient electron transfer, making it impossible to achieve stable cycling and capacity contribution. Restricted catalysis provides a solution for inhibiting the shuttle of soluble lithium polysulfides. Herein, MXene aerogel with optimized channel utilization is designed as S host according to the polysulfide control strategy of localization, adsorption, and catalysis. With the help of the results of oriented channels, the polysulfide conversion process is optimized, providing a comprehensive scheme for inhibiting the shuttle effect. Lithium sulfur catalytic batteries have achieved high capacity and stable cycling. This system provides a comprehensive solution for lithium sulfur reaction catalysis and a new perspective for the functional application of MXene based lithium sulfur batteries.

Mo2C-Co heterostructure with carbon nanosheets decorated carbon microtubules: Different means for high-performance lithium-sulfur batteries

The practical applications of lithium sulfur batteries (LSBs) are hindered by notorious shuttle effect and sluggish conversion kinetics of intermediate polysulfides. Herein, Mo2C-Co heterogeneous particles decorated two-dimensional (2D) carbon nanosheets grown on hollow carbon microtubes (CCC@MCC) are synthesized. Three-dimensional (3D) carbon framework with Mo2C-Co heterogeneous particles combines the conductivity, adsorption and catalysis, effectively trapping and accelerating the conversion of polysulfides. As evidenced experimentally, the hetero-structured Mo2C-Co with high Li+ diffusion coefficient enables uniform precipitation and complete oxidation of Li2S. Meanwhile, CCC@MCC is found to have multiple application possibilities for lithium-sulfur batteries. As an interlayer, the cells deliver an excellent capacity of 881.1 mAh/g at 2C and still retain 438.2 mAh/g after 500 cycles under the low temperature of 0 ℃. As a sulfur carrier, the cell with a sulfur loading of 7.0 mg cm−2 exhibits a high area capacity of 5.3 mAh cm−2. This work provides an effective strategy to prepare heterostructured material and imaginatively exploit the application potential of it.

Promoting polysulfides conversion by hexagonal-like V-MOF-derived VC-doped carbon nanotubes for lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) are one of the representatives of a new generation of high-performance batteries, due to their large theoretical specific discharge capacity, high energy density and low cost et al. However, shuttle effect and slow conversion kinetics of polysulfides (LiPSs) hinder the performance of LSBs. In order to mitigate shuttle effect, metal-organic frameworks are introduced. Carbon nanotubes (CNTs) is used as composite cathode, due to their high electrical conductivity. V-MOF/CNTs-derived hexagonal VC/CNTs nanosheets are successfully synthesized and used as the sulfur host. VC/CNTs nanosheet with mesoporous structure can provide a lot of active sites. VC nanosheets are uniformly distributed and interconnected with CNTs to form a conductive network structure. VC/CNTs has excellent chemical adsorption and catalytic properties on polysulfides, which can improve the redox reaction kinetics and the adsorption capability. Due to the synergistic effects, S/VC/CNTs has an excellent cycling stability. S/VC/CNTs shows a significant initial specific capacity of 1370 mAh g−1 at 0.1 C. Capacity decay rate per cycle is about 0.037 % After 500 cycles at 0.5 C, the Coulomb efficiency is nearly to 100 %. The results show that the introduction of VC/CNTs composites with special hexagonal structure can accelerate the catalytic electrochemical reaction, and the dissolution and diffusion of polysulfides are well controlled.

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.

The Impact of Oxygen Content in O-Doped MoS2 on the Kinetics of Polysulfide Conversion in Li-S Batteries.

Polysulfide shuttle and sluggish sulfur redox kinetics remain key challenges in lithium-sulfur batteries. Previous researches have shown that introducing oxygen into transition metal sulfides helps to capture polysulfides and enhance their conversion kinetics. Based on this, further investigations are conducted to explore the impact of oxygen doping levels on the physical-chemical properties and electrocatalytic performance of MoS2. The findings reveal that MoS2 doped with high-content oxygen exhibits enhanced conductivity and polysulfides conversion kinetics compared to MoS2 with low-content oxygen doping, which can be attributed to the alteration of crystal structure from 2H-phase to the 1T-phase, the introduction of increased Li-O interactions, and the effect of defects resulting from high-oxygen doping. Consequently, the lithium-sulfur batteries using high-oxygen doped MoS2 as a catalyst deliver a high discharge capacity of 1015 mAh g-1 at 0.25C and maintain 78.5% capacity after 300 more cycles. Specifically, lithium-sulfur batteries employing paper-based electrodedemonstrate an areal capacity of 3.91 mAh cm-2 at 0.15C, even with sulfur loading of 4.1mg cm-2 and electrolyte of 6.7µL mg-1. These results indicate that oxygen doping levels can modify the properties of MoS2, and high-oxygen doped MoS2 shows promise as an efficient catalyst for lithium-sulfur batteries.

Self-assembled 3D CoSe-based sulfur host enables high-efficient and durable electrocatalytic conversion of polysulfides for flexible lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are considered as promising candidates for next-generation energy storage systems. However, the commercial applications are severely limited by the sluggish kinetics and shuttling effect. Herein, we have designed an integrated free-standing functional CoSe-CNF-GO-MXene (CCGM) sulfur host with a “point-line-plane” 3D porous structure for Li-S batteries. The two-dimensional (2D) graphene, MXene and one-dimensional (1D) nanocellulose fibers combined with zero-dimensional (0D) transition metal selenide (CoSe) shows good electrical conductivity and enhanced catalytic performance, respectively. Additionally, the rationally designed porous structure (from 0D to 3D) demonstrates well-connected ion/electron transport channels, conferring the good kinetic performance. Electrochemical tests show that CoSe catalytic materials with moderate adsorption energies can catalyse both precipitation and dissolution processes of Li2S, enabling fast conversion kinetics. The density functional theory (DFT) calculations show that the synergistic effect of CoSe, Ti3C2Tx, and graphene can improve the chemisorption and catalytic performance. As a result, the 3D porous S@CCGM cathode exhibits a high initial discharge capacity of 1205.1 mAh g−1 at 0.2C and good long-term cycling performance with a low decay rate of 0.055 % per cycle at 1C. Furthermore, the gel electrolyte Li-S pouch cell successfully passes the 0–180° bending test, nailing test, and cutting test. Such design offers a new perspective for the commercialization of safe and flexible electrochemical energy-storage devices especially in Li-S batteries.

Ni/Ni4N nanoparticles anchored on 3D necklace-like carbon framework as free-standing bifunctional host for practical Li-S full cells

Inhibiting the shuttle effect, accelerating sulfur redox kinetics and controlling lithium homogeneous deposition are significant to achieve the flexible lithium-sulfur (Li-S) cells with high energy density and safety. In this study, we successfully synthesized a three-dimensional (3D) free-standing necklace-like fabric consisting of heterostructured Ni/Ni4N nanoparticles confined into hollow carbon cages implanted with N-doped carbon nanofibers (Ni/Ni4N@NCC). This unique 3D necklace-like framework and interface electronic structure of Ni/Ni4N@NCC could effectively addresses the challenges associated with both sulfur cathode and lithium anode in Li-S cells. Combine with experimental tests and DFT simulations, Ni/Ni4N@NCC not only strengthened chemical anchoring and accelerated lithium polysulfides conversion, but also induced Li uniform deposition and growth due to its excellent lithiophilicity and low Li diffusion energy barrier. For the anode, the lithium foil coating with Ni/Ni4N@NCC interlayer (denoted as Li-Ni/Ni4N@NCC anode) showed exceptional long-term cycling stability over 1000 h at the high current density of 5 mA cm−2 for high areal capacity of 5 mAh cm−2. The S-Ni/Ni4N@NCC||Li-Ni/Ni4N@NCC cell with sulfur loading (6.8mg cm−2) exhibited high areal capacities of 6.11 mAh cm−2. The synergetic effect of fascinating necklace-like structure and heterogeneous interface offer instruction for the practically viable design of high-performance flexible Li-S full cells.

Flash Joule Heating: A Promising Method for Preparing Heterostructure Catalysts to Inhibit Polysulfide Shuttling in Li-S Batteries.

The "shuttle effect" issue severely hinders the practical application of lithium-sulfur (Li-S) batteries, which is primarily caused by the significant accumulation of lithium polysulfides in the electrolyte. Designing effective catalysts is highly desired for enhancing polysulfide conversion to address the above issue. Here, the one-step flash-Joule-heating route is employed to synthesize a W-W2C heterostructure on the graphene substrate (W-W2C/G) as a catalytic interlayer for this purpose. Theoretical calculations reveal that the work function difference between W (5.08eV) and W2C (6.31eV) induces an internal electric field at the heterostructure interface, accelerating the movement of electrons and ions, thus promoting the sulfur reduction reaction (SRR) process. The high catalytic activity is also confirmed by the reduced activation energy and suppressed polysulfide shuttling by in situ Raman analyses. With the W-W2C/G interlayer, the Li-S batteries exhibit an outstanding rate performance (665 mAh g-1 at 5.0 C) and cycle steadily with a low decay rate of 0.06% over 1000 cycles at a high rate of 3.0 C. Moreover, a high areal capacity of 10.9 mAh cm-2 (1381.4 mAh g-1) is obtained with a high area sulfur loading of 7.9mg cm-2 but a low electrolyte/sulfur ratio of 9.0 µL mg-1.

Facile construction of porous carbon fibers from coal pitch for Li-S batteries

Coal pitch, an important by-product in the coal coking industry with a high output, is a low-cost and high-carbon yield precursor for the manufacturing of high-value carbon materials. Herein, N/O co-doped carbon fiber (CFCP), fabricated by electrospinning using pre-oxidized coal pitch as the precursor, was employed as the sulfur host for Li-S batteries. The presence of more pyrrolic N and graphic N in CFCP than carbon fiber made from polyacrylonitrile benefits the adsorption of lithium polysulfide and the battery’s life. Sulphur-CFCP cathode (S@CFCP) exhibited excellent specific capacity and cyclability, with a specific capacity of 701.1 mAh/g and a low capacity decay rate of 0.088% per cycle over 200 cycles at 2.0 C, respectively. The high ion diffusion rate, low charge transfer resistance, and effective conversion of lithium polysulfides enable the high electrochemical performance of S@CFCP.

Boron-Doped Dinickel Phosphide to Enhance Polysulfide Conversion and Suppress Shuttling in Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are promising for next-generation high-energy energy storage systems. However, the slow reaction kinetics render mobile polysulfides hardly controlled, yielding shuttling effects and eventually damaging Li metal anodes. To improve the cyclability of Li-S batteries, high-efficiency catalysts are desired to accelerate polysulfide conversion and suppress the shuttling effect. Herein, we studied a doping system with Ni2P and Ni2B as the end members and found a B-doped Ni2P catalyst that demonstrates high activity for Li-S batteries. As anionic dopants, B demonstrates an interesting reverse electron transfer to P and tunes the electronic structure of Ni2P dramatically. The resultant B-doped Ni2P exhibits short Ni-B bonds and strong Ni-S interaction, and the electron donation of B to P further enhances the adsorption of polysulfide on catalysts. The S-S bonds of polysulfides were activated appropriately, therefore decreasing a low energy barrier for conversion reactions.

Co3V2O8 composite carbon hollow spheres bidirectionally catalyze the conversion of lithium polysulfide to improve the capacity of lithium‐sulfur batteries

Although lithium‐sulfur batteries have a high theoretical energy density that is higher than lithium‐ion batteries, their development is limited by the slow kinetics of lithium polysulfide conversion. In this research, we utilize the excellent bidirectional catalysis and adsorption of lithium polysulfide by the bimetallic oxide Co3V2O8 composite carbon hollow sphere to address the kinetic obstacle of lithium‐sulfur battery. On the one hand, the carbon hollow sphere substrate provides a cavity that can hold a large amount of sulfur. On the other hand, it can limit the diffusion of lithium polysulfide by van der Waals forces. The combination of the above two points improves the capacity and stability of lithium‐sulfur batteries. It has a specific capacity of 1237.2 mAh g‐1 at 0.2 C current density and retains 603 mAh g‐1 after 100 cycles. At a high current density of 2 C, the specific capacity is 976.2 mAh g‐1. After 1000 cycles, it holds at 338.3 mAh g‐1, and the capacity retention rate per cycle is 99.89%. This work discovers the new potential of Co3V2O8 as an electrocatalyst and proposes a process that can widely prepare carbon materials with complex uniform distribution of electrocatalysts to achieve high specific capacity of lithium‐sulfur batteries.

Densely Branched Carbon Nanotubes for Boosting the Electrochemical Performance of Li-S Batteries.

To address the inherent limitations of conventional carbon nanotubes (CNTs), such as their tendency to agglomerate and scarcity of catalytic sites, the development of branched carbon nanotubes (BCNTs) with a unique hierarchical structure has emerged as a promising solution. Herein, gram scale quantities of densely branched and structurally consistent Ni-Fe decorated branched CNTs (Ni-Fe@BCNT) have been prepared. This uniform and densely branched architecture ensures excellent dispersibility and superior electrical conductivity. Additionally, each branched tip is equipped with Ni-Fe particles, thereby providing numerous catalytic sites which endow them with exceptional catalytic activity for the conversion of polysulfides. The polypropylene (PP) separator modified with Ni-Fe@BCNT interlayer is fabricated as a multifunctional barrier for Li-S batteries. The experimental results demonstrate that Ni-Fe@BCNT interlayer can effectively suppress the shuttle effect of polysulfides and enhance their redox kinetics. The outstanding catalytic ability of Ni-Fe@BCNT interlayer enables batteries with high specific capacities, outstanding rate performance, and remarkable cycling stability. This approach proposed in this work paves a new path for synthesizing BCNTs and shows great potential for scaling up the production of BCNTs to address more demanding applications.

High-Entropy Metal Nitride Embedded in Concave Porous Carbon Enabling Polysulfide Conversion in Lithium-Sulfur Batteries.

The practical implementation of lithium-sulfur batteries is severely hindered by the rapid capacity fading due to the solubility of the intermediate lithium polysulfides (LiPSs) and the sluggish redox kinetics. Herein, high-entropy metal nitride nanocrystals (HEMN) embedded within nitrogen-doped concave porous carbon (N-CPC) polyhedra are rationally designed as a sulfur host via a facile zeolitic imidazolate framework (ZIF)-driven adsorption-nitridation process toward this challenge. The configuration of high-entropy with incorporated metal manganese (Mn) and chromium (Cr)will optimize the d-band center of active sites with more electrons occupied in antibonding orbitals, thus promoting the adsorption and catalytic conversion of LiPSs. While the concave porous carbon not only accommodates the volume change upon the cycling processes but also physically confines and exposes active sites for accelerated sulfur redox reactions. As a result, the resultant HEMN/N-CPC composites-based sulfur cathode can deliver a high specific capacity of 1274 mAh g-1 at 0.2C and a low capacity decay rate of 0.044% after 1000 cycles at 1C. Moreover, upon sulfur loading of 5.0mg cm-2, the areal capacity of 5.0mAhcm-2 can still be achieved. The present work may provide a new avenue for the design of high-performance cathodes in Li-S batteries.

A Multifunctional Secondary Based on Heterogeneous Co-MnO@NC for Depth-Induced Deposition and Conversion of Polysulfides in Li─S Batteries.

The conductive carbon-based interlayer, as the secondary current collector in the self-dissolving battery system, can effectively capture escaping cathode active materials, inducing deep release of remaining capacity. In the multi-step reactions of Li─S batteries, the environmental tolerance of the conductive carbon-based interlayer to polysulfides determines the inhibition of shuttle effects. Here, a modified metal-organic framework (Mn-ZIF67) is utilized to obtain nitrogen-doped carbon-coated heterogeneous Co-MnO (Co-MnO@NC) with dual catalytic center for the functional interlayer materials. The synergistic coupling mechanism of NC and Co-MnO achieves rapid deposition and conversion of free polysulfide and fragmented active sulfur on the secondary current collector, reducing capacity loss in the cathode. The Li─S battery with Co-MnO@NC/PP separator maintains an initial capacity of 1050mAhg-1 (3C) and excellent cycle stability (0.056% capacity decay rate). Under extreme testing conditions (S load = 5.82mgcm-2, E/S=9.1µLmg-1), a reversible capacity of 501.36mAhg-1 is observed after 200 cycles at 0.2C, showing good further practical reliability. This work demonstrates the advancement application of Co-MnO@NC bimetallic heterojunctions catalysts in the secondary current collector for high-performance Li─S batteries, thereby providing guidance for the development of interlayer in various dissolution systems.

Steering sulfur reduction kinetics of lithium-sulfur batteries by interfacial microenvironment modulation

Catalytic conversion of lithium polysulfides (LiPSs) is considered as an effective avenue to suppress the shuttle effect of lithium-sulfur (Li-S) batteries, for which the interfacial microenvironment constructed by the interaction between electrocatalysts and LiPSs plays a pivotal role in modulating the sulfur reduction kinetics. However, most of previous reports mainly focused on modulating the band structure of electrocatalysts or LiPSs alone to enhance the catalytic activity rather than considering the interfacial microenvironment as a whole. Herein, we propose a binary descriptor composed of the energy difference between d-band of electrocatalysts and p-band of LiPSs (ΔεM-S) and the antibonding filling degree (εABF), which capture the energy band contributions from both electrocatalysts and LiPSs, to reveal the influence of interfacial microenvironment on sulfur reduction kinetics. Among different designed electrocatalysts, NiO presents a moderate LiPSs anchoring capacity and rapid electron transfer kinetics owing to the optimal ΔεM-S and decreased εABF after interacting with LiPSs, which lead to a robust interfacial microenvironment and thus guarantee a continuous catalytic conversion of LiPSs in the long-term cycling. Such a fundamental understanding of catalytic activity toward LiPSs from the viewpoint of interfacial microenvironment provides an alternative avenue for designing highly efficient electrocatalysts for Li-S batteries.

Activation of MOF Catalysts with Low Steric Hindrance via Undercoordination Chemistry for Efficient Polysulfide Conversion in Lithium–Sulfur Battery

AbstractLithium–sulfur (Li–S) batteries promise high theoretical energy density and cost‐effectiveness but grapple with challenges like the polysulfide shuttle effect and sluggish kinetics. Metal–organic framework (MOF) catalysts emerge as a leading solution, despite limited conductivity and high steric hindrance. This study employs undercoordination chemistry to modify Zn–Co bimetallic MOFs (D‐ZIF L), removing organic ligands from active centers. This process mitigates spatial hindrance, thereby promoting comprehensive contact between sulfur species and metal active centers, consequently enhancing the catalytic efficiency of MOFs. Moreover, undercoordination treatment of the metal active centers induces electron redistribution, augmenting electron density at the Fermi level of the metal elements, thereby ameliorating the intrinsic conductivity. Leveraging these advantages, fabricated Li–S batteries employing D‐ZIF L catalysts exhibited markedly mitigated shuttling effects and accelerated sulfur species conversion kinetics. Notably, a substantial reverse areal capacity of 5.0 mAh cm⁻2 is achieved after 100 cycles with an evaluated sulfur loading of 5.5 mg cm⁻2. Furthermore, a practical pouch cell demonstrated an initial capacity of 1.8 Ah at 85.8 mA with stable cycling for 50 cycles. This study underscores the potential of undercoordination chemistry in the development of highly conductive MOF catalysts with minimized steric hindrance, thereby advancing the prospects of Li–S battery technology.

Amorphous FeSnOx Nanosheets with Hierarchical Vacancies for Room-Temperature Sodium-Sulfur Batteries.

Room-temperature sodium-sulfur (RT Na-S) batteries, noted for their low material costs and high energy density, are emerging as a promising alternative to lithium-ion batteries (LIBs) in various applications including power grids and standalone renewable energy systems. These batteries are commonly assembled with glass fiber membranes, which face significant challenges like the dissolution of polysulfides, sluggish sulfur conversion kinetics, and the growth of Na dendrites. Here, we develop an amorphous two-dimensional (2D) iron tin oxide (A-FeSnOx) nanosheet with hierarchical vacancies, including abundant oxygen vacancies (Ovs) and nano-sized perforations, that can be assembled into a multifunctional layer overlaying commercial separators for RT Na-S batteries. The Ovs offer strong adsorption and abundant catalytic sites for polysulfides, while the defect concentration is finely tuned to elucidate the polysulfides conversion mechanisms. The nano-sized perforations aid in regulating Na ions transport, resulting in uniform Na deposition. Moreover, the strategic addition of trace amounts of Ti3C2 (MXene) forms an amorphous/crystalline (A/C) interface that significantly improves the mechanical properties of the separator and suppresses dendrite growth. As a result, the task-specific layer achieves ultra-light (~0.1 mg cm-2), ultra-thin (~200 nm), and ultra-robust (modulus=4.9 GPa) characteristics. Consequently, the RT Na-S battery maintained a high capacity of 610.3 mAh g-1 and an average Coulombic efficiency of 99.9 % after 400 cycles at 0.5 C.