Room-temperature Sodium-sulfur Batteries Research Articles

Amorphous FeSnOxNanosheets 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 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 dendrites growth. Here, we develop an amorphous 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 forms an amorphous/crystalline interface that significantly improves the mechanical properties of the separator and suppresses dendrite growth. As a result, the task-specific layer achieves ultra-light (~0.1mg cm-2), ultra-thin (~200nm), and ultra-robust (modulus = 4.9GPa) characteristics. Consequently, the RT Na-S battery maintained a high capacity of 610.3mAh g-1 and an average Coulombic efficiency of 99.9% after 400 cycles at 0.5C.

A Polysulfides‐Defensive, Dendrite‐Suppressed, and Flame‐Retardant Separator with Lean Electrolyte for Room Temperature Sodium–Sulfur Batteries

AbstractThe dissolution/shuttling of sodium polysulfides, coupled with sodium dendrites growth, severely compromises the lifespan and stability of room temperature sodium–sulfur (RT Na–S) batteries. Herein, it proposes employing a functionalized porous ZIF‐based membrane (PZM) to address these two challenges. First, the metal ions embedded within the zeolitic imidazolate framework chemically bind with polysulfide anions, curtailing their detrimental shuttling. Second, the tailored porous structure of the membrane ensures a selective and uniform pathway for sodium ions, significantly reducing non‐uniform deposition and curbing dendritic sodium growth. Third, the intrinsically non‐combustible nature of the ZIF‐based membrane acts as a fortification against thermal outbursts and electrolyte decomposition. Implementing this polysulfide‐resistant, dendrite‐inhibiting and flame‐retardant PZM with a standard S/C cathode leads to the creation of a robust separator with lean electrolyte RT Na–S battery. This configuration may impart a novel perspective for the advancement and enhancement of RT Na–S battery systems.

Accelerating Na2S/Na2S2 conversion kinetics by electrolyte additive with high Na2S/Na2S2 solubility for high-performance room-temperature sodium–sulfur batteries

The development of room-temperature sodium sulfur batteries is severely constrained by the sluggish solid-solid conversion kinetics of Na2S/Na2S2 and the accumulation of “dead Na2S/Na2S2”. Here, we accelerate the conversion kinetics of Na2S/Na2S2 as well as reduce the accumulation of “dead Na2S/Na2S2” by 1-butyl-1-methylpyrrolidine trifluoromethanesulfonate ([P14][OTf]) ionic liquid additive that is compatible with metallic Na and has high Na2S/Na2S2 solubility. The results of three-electrode kinetics tests show a significant enhancement of the apparent redox kinetics of Na2S/Na2S2 through increasing its concentration. During battery cycling, the increase in Na2S/Na2S2 concentration can induce the formation of three-dimensional Na2S deposition and reduce the coverage of the electrode effective electroactive area, thus decreasing the battery polarization, especially at high rates. In addition, high Na2S/Na2S2 solubility can promote the reuse of “dead Na2S/Na2S2” and greatly improve the utilization of active material. At 2C rate, 351 mAh g−1 can be maintained after 800 cycles, and the capacity decay per cycle is 0.046 %. The rate and cycle performance of the battery are greatly improved. Further, a mechanism is proposed for the enhancement of battery performance via overpotential and diffusion theories.

Understanding the charge transfer effects of single atoms for boosting the performance of Na-S batteries.

The effective flow of electrons through bulk electrodes is crucial for achieving high-performance batteries, although the poor conductivity of homocyclic sulfur molecules results in high barriers against the passage of electrons through electrode structures. This phenomenon causes incomplete reactions and the formation of metastable products. To enhance the performance of the electrode, it is important to place substitutable electrification units to accelerate the cleavage of sulfur molecules and increase the selectivity of stable products during charging and discharging. Herein, we develop a single-atom-charging strategy to address the electron transport issues in bulk sulfur electrodes. The establishment of the synergistic interaction between the adsorption model and electronic transfer helps us achieve a high level of selectivity towards the desirable short-chain sodium polysulfides during the practical battery test. These finding indicates that the atomic manganese sites have an enhanced ability to capture and donate electrons. Additionally, the charge transfer process facilitates the rearrangement of sodium ions, thereby accelerating the kinetics of the sodium ions through the electrostatic force. These combined effects improve pathway selectivity and conversion to stable products during the redox process, leading to superior electrochemical performance for room temperature sodium-sulfur batteries.

Enhancing Conversion Kinetics through Electron Density Dual-Regulation of Catalysts and Sulfur toward Room-/Subzero-Temperature Na-S Batteries.

Room-temperature sodium-sulfur (RT Na/S) batteries have received increasing attention for the next generation of large-scale energy storage, yet they are hindered by the severe dissolution of polysulfides, sluggish redox kinetic, and incomplete conversion of sodium polysulfides (NaPSs). Herein, the study proposes a dual-modulating strategy of the electronic structure of electrocatalyst and sulfur to accelerate the conversion of NaPSs. The selenium-modulated ZnS nanocrystals with electron rearrangement in hierarchical structured spherical carbon (Se-ZnS/HSC) facilitate Na+ transport and catalyze the conversion between short-chain sulfur and Na2S. And the in situ introduced Se within S can enhance conductivity and form an S─Se bond, suppressing the "polysulfides shuttle". Accordingly, the S@Se-ZnS/HSC cathode exhibits a specific capacity of as high as 1302.5 mAh g-1 at 0.1 A g-1 and ultrahigh-rate capability (676.9 mAh g-1 at 5.0 A g-1). Even at -10 °C, this cathode still delivers a high reversible capacity of 401.2 mAh g-1 at 0.05 A g-1 and 94% of the original capacitance after 50 cycles. This work provides a novel design idea for high-performance Na/S batteries.

Designing Urchin-Like S@SiO2 with Regulated Pores Toward Ultra-Fast Room Temperature Sodium-Sulfur Battery.

Captured by high theoretical capacity and low-cost, Sodium-Sulfur (Na-S) batteries have been deemed as promising energy-storage systems. However, their electrochemical properties, containing both cycling and rate properties, still suffer from the notorious "shuttle effect" of polysulfide. Herein, through the effective regulation of pore sizes, a series of S@SiO2 cathode materials are obtained. Benefitting from the abundant pore channels of SiO2 particles, the sulfur loading is as high as 76.3%. Importantly, a suitable pore size can lead to adequate reaction and rapid diffusion behaviors, resulting in excellent electrochemical performances. Specifically, at 2.0Ag-1, the initial capacity of the as-optimized sample can be up to 1370.6mAhg-1. Surprisingly, even after 1050 cycles, it could achieve a high reversible capacity of 1280.8mAhg-1 with an attenuation rate of 0.089%. At 5.0Ag-1, after 500 cycles, the capacity can still remain ≈ 1132.6mAhg-1 (capacity retention rate, 97.5%). Given this, the work is anticipated to offer an effective strategy for advanced electrodes for Na-S batteries.

Nitrogen-doped porous carbon hosted sulfur-rich polymer for room temperature Na-S batteries with superior cycle performances

Room temperature sodium-sulfur (RT Na-S) batteries are one of the most promising energy storage systems with high energy density due to the abundant reserves of sodium and sulfur elements on Earth. As a potential cathode material, sulfur-rich polymers are rarely reported in RT Na-S batteries compared with other metal-sulfur batteries. The unusual occurrence is a result of sulfur-rich polymer cathodes failing in Na-S batteries. To reverse the process, herein, we first illuminate the failure mechanism of sulfur-rich polymer cathodes (S-DIB as an example) in Na-S batteries, which root from the chemical reaction between the polysulfide and the sodium anode. To address this issue, we incorporate nitrogen-doped carbon (NC) into composites with S-DIB to establish ion diffusion pathways and limit polysulfide diffusion. The resulting S-DIB@NC composite demonstrates exceptional cycling performance, achieving a high capacity of 457 mA h g-1 after 1300 cycles. This research constitutes a significant step towards enhancing the viability of sulfur-rich polymers in Na-S batteries and paves the way for their widespread application.

A Critical Review on Room-Temperature Sodium-Sulfur Batteries: From Research Advances to Practical Perspectives.

Room-temperature sodium-sulfur (RT-Na/S) batteries are promising alternatives for next-generation energy storage systems with high energy density and high power density. However, some notorious issues are hampering the practical application of RT-Na/S batteries. Besides, the working mechanism of RT-Na/S batteries under practical conditions such as high sulfur loading, lean electrolyte, and low capacity ratio between the negative and positive electrode (N/P ratio), is of essential importance for practical applications, yet the significance of these parameters has long been disregarded. Herein, it is comprehensively reviewed recent advances on Na metal anode, S cathode, electrolyte, and separator engineering for RT-Na/S batteries. The discrepancies between laboratory research and practical conditions are elaborately discussed, endeavors toward practical applications are highlighted, and suggestions for the practical values of the crucial parameters are rationally proposed. Furthermore, an empirical equation to estimate the actual energy density of RT-Na/S pouch cells under practical conditions is rationally proposed for the first time, making it possible to evaluate the gravimetric energy density of the cells under practical conditions. This review aims to reemphasize the vital importance of the crucial parameters for RT-Na/S batteries to bridge the gaps between laboratory research and practical applications.

A Highly Dispersed Cobalt Electrocatalyst with Electron-Deficient Centers Induced by Boron toward Enhanced Adsorption and Electrocatalysis for Room-Temperature Sodium-Sulfur Batteries.

As vitally prospective candidates for next-generation energy storage systems, room-temperature sodium-sulfur (RT-Na/S) batteries continue to face obstacles in practical implementation due to the severe shuttle effect of sodium polysulfides and sluggish S conversion kinetics. Herein, the study proposes a novel approach involving the design of a B, N co-doped carbon nanotube loaded with highly dispersed and electron-deficient cobalt (Co@BNC) as a highly conductive host for S, aiming to enhance adsorption and catalyze redox reactions. Crucially, the pivotal roles of the carbon substrate in prompting the electrocatalytic activity of Co are elucidated. The experiments and density functional theory (DFT) calculations both demonstrate that after B doping, stronger chemical adsorption toward polysulfides (NaPSs), lower polarization, faster S conversion kinetics, and more complete S transformation are achieved. Therefore, the as-assembled RT-Na/S batteries with S/Co@BNC deliver a high reversible capacity of 626 mAh g-1 over 100 cycles at 0.1 C and excellent durability (416 mAh g-1 over 600 cycles at 0.5 C). Even at 2 C, the capacity retention remains at 61.8%, exhibiting an outstanding rate performance. This work offers a systematic way to develop a novel Co electrocatalyst for RT-Na/S batteries, which can also be effectively applied to other transition metallic electrocatalysts.

Linearly Interlinked Fe-Nx -Fe Single Atoms Catalyze High-Rate Sodium-Sulfur Batteries.

Linearly interlinked single atoms offer unprecedented physiochemical properties, but their synthesis for practical applications still poses significant challenges. Herein, linearly interlinked iron single-atom catalysts that are loaded onto interconnected carbon channels as cathodic sulfur hosts for room-temperature sodium-sulfur batteries are presented. The interlinked iron single-atom exhibits unique metallic iron bonds that facilitate the transfer of electrons to the sulfur cathode, thereby accelerating the reaction kinetics. Additionally, the columnated and interlinked carbon channels ensure rapid Na+ diffusion kinetics to support high-rate battery reactions. By combining the iron atomic chains and the topological carbon channels, the resulting sulfur cathodes demonstrate effective high-rate conversion performance while maintaining excellent stability. Remarkably, even after 5000 cycles at a current density of 10 A g-1 , the Na-S battery retains a capacity of 325 mAh g-1 . This work can open a new avenue in the design of catalysts and carbon ionic channels, paving the way to achieve sustainable and high-performance energy devices.

Tailoring Na+ Solvation Environment and Electrode-Electrolyte Interphases with Sn(OTf)2 Additive in Non-flammable Phosphate Electrolytes towards Safe and Efficient Na-S Batteries.

Room-temperature sodium-sulfur (RT Na-S) batteries are promising for low-cost and large-scale energy storage applications. However, these batteries are plagued by safety concerns due to the highly flammable nature of conventional electrolytes. Although non-flammable electrolytes eliminate the risk of fire, they often result in compromised battery performance due to poor compatibility with sodium metal anode and sulfur cathode. Herein, we develop an additive of tin trifluoromethanesulfonate (Sn(OTf)2 ) in non-flammable phosphate electrolytes to improve the cycling stability of RT Na-S batteries via modulating the Na+ solvation environment and interface chemistry. The additive reduces the Na+ desolvation energy and enhances the electrolyte stability. Moreover, it facilitates the construction of Na-Sn alloy-based anode solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI). These interphases help to suppress the growth of Na dendrites and the dissolution/shuttling of sodium polysulfides (NaPSs), resulting in improved reversible capacity. Specifically, the Na-S battery with the designed electrolyte boosts the capacity from 322 to 906 mAh g-1 at 0.5 A g-1 . This study provides valuable insights for the development of safe and high-performance electrolytes in RT Na-S batteries.

Heterostructured Co/CeO2-Decorating N-Doped Porous Carbon Nanocubes as Efficient Sulfur Hosts with Enhanced Rate Capability and Cycling Durability toward Room-Temperature Na-S Batteries.

Room-temperature sodium-sulfur (RT Na-S) batteries have gained significant interest thanks to their satisfactory energy density and abundant earth resources. Nevertheless, practical implementations of RT Na-S batteries are still impeded by serious shuttle effects of sodium polysulfide (NaPS) intermediates, sluggish redox kinetics of cathodes, and poor electronic conductivity from S-species. To solve these problems, heterostructured Co/CeO2-decorating N-doped porous carbon nanocubes (Co/CeO2-NPC) are constructed as a S support, which integrates the strong adsorption and fast conversion of NaPSs, together with superior electronic conductivity. Consequently, the as-synthesized S@Co/CeO2-NPC cathode for RT Na-S batteries exhibits improved rate performance (1275, 561.1, and 485 mAh g-1 at 0.1, 5, and 10 C, respectively) and superior cyclic durability (capacity degeneration of 0.027% per cycle after 1000 cycles at 5 C). Such a S cathode combining a heterostructure interface, hierarchical porous carbon nanocubes, and polar compositions can considerably increase electronic conductivity and promote NaPS adsorption and conversion, achieving superior performance toward RT Na-S batteries.

A Mott-Schottky Heterojunction with Strong Chemisorption and Fast Conversion Effects for Room-Temperature Na-S Batteries.

The practical application of the room-temperature sodium-sulfur (RT Na-S) batteries is currently limited by low reversible capacity and serious capacity decay due to the sluggish reaction kinetics and shuttle effect. It is necessary to design a suitable sulfur host integrated with electrocatalysts to realize effective chemisorption and catalysis of sodium polysulfides (NaPSs). Herein, under the guidance of theoretical calculation, the Mott-Schottky heterojunction with a built-in electric field composed of iron (Fe) and iron disulfide (FeS2 ) components anchored on a porous carbon matrix (Fe/FeS2 -PC) is designed and prepared. The enhanced chemisorption effect of Fe, the fast electrocatalytic effect of FeS2 , and the fast transfer effect of the built-in electric field within the Fe/FeS2 heterojunction in the cathode of RT Na-S batteries work together to effectively improve the electrochemical performance. As a result, the Fe/FeS2 -PC@S cathode exhibits high reversible capacity (815 mAh g-1 after 150 cycles at 0.2 A g-1 ) and excellent stability (516 mAh g-1 after 600 cycles at 5 A g-1 , with only 0.07% decay per cycle). The design of the Fe/FeS2 heterojunction electrocatalyst provides a new strategy for the development of highly stable RT Na-S batteries.

Defect engineering of a TiO2 anatase/rutile homojunction accelerating sulfur redox kinetics for high-performance Na-S batteries.

Room-temperature sodium-sulfur (RT Na-S) batteries have the drawbacks of the poor shuttle effect of soluble sodium polysulfides (NaPSs) as well as slow sulfur redox kinetics, which result in poor cycling stability and low capacity, seriously affecting their extensive application. Herein, defect engineering is applied to construct rich oxygen vacancies at the interface of a TiO2 anatase/rutile homojunction (OV-TRA) to enhance sulfur affinity and redox reaction kinetics. Combining structural characterizations with electrochemical analysis reveals that OV-TRA well alleviates the shuttle effect of NaPSs and precipitates the deposition and diffusion kinetics of Na2S. Consequently, S/OV-TRA provides excellent electrochemical performance with a reversible capacity of 870 mA h g-1 at 0.1 C after 100 cycles and a long-term cycling capability of 759 mA h g-1 at 1 C after 1000 cycles. This work provides an effective interfacial defect engineering strategy to promote the application of metal oxides in RT Na-S batteries.

Mechanism and Kinetics of Na2Sx (x ≤ 2) Precipitation in Sodium-Sulfur and Sodium/(Oxygen)-Sulfur Batteries

Room-temperature sodium-sulfur (RT Na-S) batteries have attracted ever-increasing attention because of their enhanced energy density and low price. Although the performance of RT Na-S batteries is obtained in many other research, the basic mechanism and kinetics have not involved yet, especially in discharge product growth, which affects electrochemical performance. Meanwhile, designed additional redox activities (in the presence of oxygen) could simultaneously suppress sodium polysulfide shuttling and enhance energy density according to our group reported. However, the kinetic study of the intermediate has not been explored. In this work, we discussed the deposition of low-order sodium polysulfide (Na2Sx, x ≤ 2) in different potentials and types of glyme-solvents in Na-S and Na/(O2)-S system. The results show that the morphology of deposition Na2Sx (x ≤ 2) is affected by interfacial energy barrier controlled by overpotentials and the radius of sodium ions, which produced the precipitation of particle shape rather than film. Potentiostatic experiments show the kinetics are elevated in the presence of oxygen. In addition, the exchange current density of different sodium polysulfides was studied. The high-order sodium polysulfide has a lower exchange current density than that of low-order sodium polysulfide in Na-S system, requiring greater driving force, while transformation of the intermediate from high-order oxy-sulfur to low-order oxy-sulfur species require less impulse in Na/(O2)-S systems. This paper provides new understandings of the deposition mechanism and kinetics of Na2Sx (x ≤ 2) Na-S and Na/(O2)-S system in and to choose the appropriate solvent and potential.

3D Flower-like Nanospheres Constructed by Transition Metal Telluride Nanosheets as Sulfur Immobilizers for High-Performance Room-Temperature Na-S Batteries.

Room-temperature sodium-sulfur (RT Na-S) batteries hold immense promise as next-generation energy storage systems, owing to their exceptionally high theoretical capacity, abundant resources, eco-friendliness, and affordability. Nevertheless, their practical application is impeded by the shuttling effect of sodium polysulfides (NaPSs) and sluggish sulfur redox kinetics. In this study, an advanced strategy by designing 3D flower-like molybdenum telluride (MoTe2 ) as an efficient catalyst to promote sulfur redox for RT Na-S batteries is presented. The unique 3D flower-like MoTe2 effectively prevents NaPS shuttling and simultaneously offers abundant active catalytic sites facilitating polysulfide redox. Consequently, the obtained MoTe2 /S cathode delivers an outstanding initial reversible capacity of 1015mAhg-1 at 0.1C, along with robust cycling stability of retaining 498mAhg-1 at 1C after 500 cycles. In addition, pouch cells are fabricated with the MoTe2 additive to deliver an ultrahigh initial discharge capacity of 890mAhg-1 and remain stable over 40 cycles under practically necessary conditions, demonstrating the potential application in the commercialization of RT Na-S batteries.

Battery Technologies in Electrochemical Energy Storage

Electrochemical energy storage technologies play a pivotal role in stabilizing renewable energy sources, ensuring a consistent power supply, and reducing our reliance on fossil fuels. In this article, three electrochemical energy storage technologies—lithium-ion batteries, sodium-sulfur batteries, and flow batteries—are analyzed and contrasted with an emphasis on their hopeful futures. Lithium-ion batteries operate by shuttling lithium ions between cathodes and anodes through an electrolyte, offering high energy density, rechargeability, stable voltage, long cycle life, and low self-discharging rate, making them versatile for a variety of uses, such as grid-scale power storage. However, cost, recycling challenges, and safety concerns have led to ongoing research into solid-state lithium-ion batteries for enhanced performance and safety. Sodium-sulfur batteries, while operating at high temperatures, provide high energy density and reliability, making them suitable for grid-level energy storage and backup power applications. Considering their shortages, researchers are exploring room-temperature sodium-sulfur batteries as a possible alternative with improved safety and cost-effectiveness for various energy storage applications, such as grid integration and electric vehicles. Flow batteries, with their separate electrolyte reservoirs, offer scalability and prolonged lifespan, making them ideal for grid-level energy storage and renewable energy integration. However, they have lower energy density and efficiency compared to some other battery types, requiring ongoing research to address these limitations and enhance their competitiveness in the energy storage market. Compared with sodium-sulfur batteries and flow batteries, lithium-ion batteries hold a dominant position due to their versatility, ongoing research advancements, and extensive infrastructure support.

Strategies to Stabilize the Sodium metal anode for High-energy Room-temperature Sodium-Sulfur Batteries

Room temperature sodium-sulfur batteries possess higher specific energy and improved inherent safety compared to their high-temperature analogs used in stationary grid storage. The viability of room temperature sodium batteries depends critically on the mechanical and ionic transport properties of the solid electrolyte interphase. Solid electrolyte interphases address a number of concomitant challenges, including large volume change, low ionic conductivity, rapid dendrite growth, and high chemical reactivity, which limit the viability of sodium anodes. In this presentation, novel strategies to stabilize the sodium metal anode are discussed that enable a high-rate cycling of sodium anodes. A solid-vapor growth approach is developed to fabricate a variety of artificial interphases directly on the surface of the sodium metal anode. As a result, the metal anode could be cycled for over 600 cycles at relatively higher currents. A room-temperature sodium-sulfur cell comprising modified sodium metal anode and sulfur cathode could be cycled for over 500 cycles with minimal capacity decay per cycle.

Chemically tuned nitrogen-doped sulfur host for a reversible and stable room-temperature sodium-sulfur batteries

The fast transition of long-chain polysulfide to short-chain polysulfide causes a sharp decay in the performance of room-temperature sodium sulfur (RT-Na/S) batteries. The nitrogen-doped sulfur host is identified as effective in slowing the transition process by entrapping the sodium polysulfide. However, precise control over the amount of nitrogen remained a challenge. We report a chemical route to fine-tune nitrogen doping in the sulfur host. The nitrogen content in the sulfur host is identified to vary from 7 to 19 at. % by varying the reaction time from 4 to 12 h. The optimized reaction time of about 8 h results in the highest pyridinic and pyrrolic nitrogen content. In addition to nitrogen doping, the sulfur host with a hierarchical pore structure could be achieved with 8 h of reaction time. The as-developed sulfur host serves as a sulfur cathode and is used to fabricate an RT-Na/S battery. The cell could function stably for over 500 cycles at 1C, with a high Coulombic efficiency of ~99.5 % and a capacity decay of 0.28 mAh g−1 per cycle at 1C. The cell could function reversibly and stably at various C-rates (0.2C – 2C). This study paves a path for the researcher to revisit the design of the sulfur host to construct a stable cathode for RT-Na/S batteries.

Polysulfide regulation by defect-modulated Ta3N5−x electrocatalyst toward superior room-temperature sodium-sulfur batteries

Resolving low sulfur reaction activity and severe polysulfide dissolution remains challenging in metal-sulfur batteries. Motivated by a theoretical prediction, herein, we strategically propose nitrogen-vacancy tantalum nitride (Ta3N5−x) impregnated inside the interconnected nanopores of nitrogen-decorated carbon matrix as a new electrocatalyst for regulating sulfur redox reactions in room-temperature sodium-sulfur batteries. Through a pore-constriction mechanism, the nitrogen vacancies are controllably constructed during the nucleation of Ta3N5−x. The defect manipulation on the local environment enables well-regulated Ta 5d-orbital energy level, not only modulating band structure toward enhanced intrinsic conductivity of Ta-based materials, but also promoting polysulfide stabilization and achieving bifunctional catalytic capability toward completely reversible polysulfide conversion. Moreover, the interconnected continuous Ta3N5−x-in-pore structure facilitates electron and sodium-ion transport and accommodates volume expansion of sulfur species while suppressing their shuttle behavior. Due to these attributes, the as-developed Ta3N5−x-based electrode achieves superior rate capability of 730 mAh g−1 at 3.35 A g−1, long-term cycling stability over 2000 cycles, and high areal capacity over 6 mAh cm−2 under high sulfur loading of 6.2 mg cm−2. This work not only presents a new sulfur electrocatalyst candidate for metal-sulfur batteries, but also sheds light on the controllable material design of defect structure in hopes of inspiring new ideas and directions for future research.