Room-temperature Sodium-sulfur Batteries Research Articles

Tunable Nitrogen-Doping of Sulfur Host Nanostructures for Stable and Shuttle-Free Room-Temperature Sodium-Sulfur Batteries.

Room-temperature sodium-sulfur batteries have potential in stationary applications, but challenges such as loss of active sulfur and low electrical conductivity must be solved. Nitrogen-doped nanocarbon host cathodes have been employed in metal-sulfur batteries: polar interactions mitigate the loss of sulfur, while the conductive nanostructure addresses the low conductivity. Nevertheless, these two properties run contrary to each other as greater nitrogen-doping of nanocarbon hosts is associated with lower conductivity. Herein, we investigate the polarity-conductivity dilemma to determine which of these properties have the stronger influence on cycling performance. Lower carbonization temperatures produce more pyridinic nitrogen and pyrrolic nitrogen, which from density functional theory calculations preferentially bind discharge products (Na2S and short-chain polysulfides). Despite its lower conductivity, the highly doped composite showed better Coulombic efficiency and stability, retaining a high capacity of 980 mAh g(S)-1 after 800 cycles. Our findings represent a paradigm shift where nitrogen-doping should be prioritized in designing shuttle-free, long-life sodium-sulfur batteries.

Strategies for Polysulfide Immobilization in Sulfur Cathodes for Room-Temperature Sodium-Sulfur Batteries.

Room-temperature sodium-sulfur batteries are one of the most attractive energy storage systems due to their low cost and ultrahigh energy density (2600 W h kg-1 ). During the charge/discharge process, the sulfur can react with sodium via a multistep redox reaction to obtain a high specific capacity (1675 mA h g-1 ). However, these batteries face the difficult challenge of the "shuttle effect," which hinders their practical application. Many strategies have been employed to address this issue on sulfur electrodes, such as intact physical confinement, chemical inhibition, and electrocatalysis. In this review, the mechanisms of the abovementioned strategies are summarized, the remaining issues are clarified, and research directions are proposed for developing advanced sodium-sulfur batteries.

Hydrothermal synthesis of MoS2/rGO composite as sulfur hosts for room temperature sodium-sulfur batteries and its electrochemical properties

The room temperature sodium-sulfur batteries are an attraction to worldwide industrial and academic as a next-generation energy storage system due to the high energy density, theoretical capacity, and cheap cost of sulfur. However, the practical application is being overdue by fast decay, poor conductivity, and the shuttle effect attributed to the low coulombic efficiency. The present study focuses on preparing MoS2/rGO/S cathode material to overcome the disadvantages of room temperature sodium-sulfur (RT-NaS) batteries. We used hydrothermal method to prepare MoS2, rGO, and MoS2/rGO composite and the sulfur was infused by the melt diffusion. The MoS2/rGO/S composite shows a high reversible capacity of 190 mAh/g after 1000 cycles at a 2 C-rate. The flower-like MoS2/rGO/S composite increases the conductivity and buffers the volume expansion during cycling.

Designing dual-defending system based on catalytic and kinetic iron Pyrite@C hybrid fibers for long-life room-temperature sodium-sulfur batteries

The poor conductivity and severe polysulfide dissolution greatly restrict the development of room-temperature sodium-sulfur (RT-Na/S) batteries. To address these issues, a dual-polysulfide-defending system based on catalytic and kinetic hybrid fibers is designed to realize high-performance and long-life for RT-Na/S batteries. The hollow carbon fibers filled with yolk-shell FeS2/C hollow nanocubes (FeS2[email protected]) are constructed as the flexible sulfur host. The highly conductive and porous network ensures fast electron/ion transports and facilitates high mass loading. More impressively, the polar FeS2 boxes ensure the strong chemical binding and high catalytic redox reaction on polysulfides, which produce the first defense on polysulfide shuttle. Meanwhile, the FeS2@C/carbon nanotubes (CNT) hybrid film works as the modifying layer on the separator, which builds the second defense to ion shuttle. Taken the advantages of both dual-polysulfide-defending system and the hierarchical polar electrode, the RT-Na/S battery achieves superior high-rate capability, long-term cycling stability and high energy storages. It obtains an ultralow capacity decay rate (0.024%) during 1000 cycles at the rate of 2C with a high mass loading of 7.6 mg cm−2. Therefore, this work not only designs a freestanding kinetic and catalytic host for sulfur electrodes, but also provides a new design on RT-Na/S batteries to realize long life, superior rate capability and high energy storage synchronously.

MOF-Derived CoS2/N-Doped Carbon Composite to Induce Short-Chain Sulfur Molecule Generation for Enhanced Sodium-Sulfur Battery Performance.

Dissolution of intermediate sodium polysulfides (Na2Sx; 4≤x≤8) is a crucial obstacle for the development of room-temperature sodium-sulfur (Na-S) batteries. One promising strategy to avoid this issue is to load short-chain sulfur (S2-4), which could prohibit the generation of soluble polysulfides during the sodiation process. Herein, unlike in the previous reported cases where short-chain sulfur was stored by confinement within a small-pore-size (≤0.5 nm) carbon host, we report a new strategy to generate short-chain sulfur in larger pores (>0.5 nm) by the synergistic catalytic effect of CoS2 and appropriate pore size. Based on density functional theory calculations, we predict that CoS2 can serve as a catalyst to weaken the S-S bond in the S8 ring structure, facilitating the formation of short-chain sulfur molecules. By experimentally tuning the pore size of the CoS2-based hosts and comparing their performances as cathodes in Na-S and Li-S batteries, we conclude that such a catalytic effect depends on the proximity of sulfur to CoS2. This avoids the generation of soluble polysulfides and results in superior electrochemical properties of the composite materials introduced here for Na-S batteries. As a result, the optimized CoS2/N-doped carbon/S electrode showed excellent electrochemical performance with high reversible specific capacities of 488 mA h g-1 (962 mA h g(s)-1) after 100 cycles (0.1 A g-1) and 403 mA h g-1 after 1000 cycles (1 A g-1) with a superior rate performance (262 mA h g-1 at 5.0 A g-1).

The promises, challenges and pathways to room-temperature sodium-sulfur batteries.

Room-temperature sodium-sulfur batteries (RT-Na-S batteries) are attractive for large-scale energy storage applications owing to their high storage capacity as well as the rich abundance and low cost of the materials. Unfortunately, their practical application is hampered by severe challenges, such as low conductivity of sulfur and its reduced products, volume expansion, polysulfide shuttling effect and Na dendrite formation, which can lead to rapid capacity fading. The review discusses the Na-S-energy-storage chemistry, highlighting its promise, key challenges and potential strategies for large-scale energy storage systems. Specifically, we review the electrochemical principles and the current technical challenges of RT-Na-S batteries, and discuss the strategies to address these obstacles. In particular, we give a comprehensive review of recent progresses in cathodes, anodes, electrolytes, separators and cell configurations, and provide a forward-looking perspective on strategies toward robust high-energy-density RT-Na-S batteries.

Recent progress on the design of hollow carbon spheres to host sulfur in room-temperature sodium–sulfur batteries

Recent progress on the design of hollow carbon spheres to host sulfur in room-temperature sodium–sulfur batteries

Research Progress toward Room Temperature Sodium Sulfur Batteries: A Review

Lithium metal batteries have achieved large-scale application, but still have limitations such as poor safety performance and high cost, and limited lithium resources limit the production of lithium batteries. The construction of these devices is also hampered by limited lithium supplies. Therefore, it is particularly important to find alternative metals for lithium replacement. Sodium has the properties of rich in content, low cost and ability to provide high voltage, which makes it an ideal substitute for lithium. Sulfur-based materials have attributes of high energy density, high theoretical specific capacity and are easily oxidized. They may be used as cathodes matched with sodium anodes to form a sodium-sulfur battery. Traditional sodium-sulfur batteries are used at a temperature of about 300 °C. In order to solve problems associated with flammability, explosiveness and energy loss caused by high-temperature use conditions, most research is now focused on the development of room temperature sodium-sulfur batteries. Regardless of safety performance or energy storage performance, room temperature sodium-sulfur batteries have great potential as next-generation secondary batteries. This article summarizes the working principle and existing problems for room temperature sodium-sulfur battery, and summarizes the methods necessary to solve key scientific problems to improve the comprehensive energy storage performance of sodium-sulfur battery from four aspects: cathode, anode, electrolyte and separator.

Enabling a Stable Room-Temperature Sodium-Sulfur Battery Cathode by Building Heterostructures in Multichannel Carbon Fibers.

Room-temperature sodium-sulfur (RT Na-S) batteries are widely considered as one of the alternative energy-storage systems with low cost and high energy density. However, the both poor cycle stability and capacity are two critical issues arising from low conversion kinetics and sodium polysulfides (NaPSs) dissolution for sulfur cathodes during the charge/discharge process. Herein, we report a highly stable RT Na-S battery cathode via building heterostructures in multichannel carbon fibers. The TiN-TiO2@MCCFs, fabricated by electrospinning and nitriding techniques, are loaded with the active material S, forming S/TiN-TiO2@MCCFs as the cathode in a RT Na-S battery. At 0.1 A g-1, the cathode produces the capacity of more than 640 mAh g-1 within 100 cycles with a high Coulombic efficiency of nearly 100%. Even at 5 A g-1, the battery still exhibites a capacity of 257.1 mAh g-1 after 1000 cycles. Combining structural and electrochemical analyses with the first-principles calculations reveals that the incorporation of the highly electrocatalytic activity of TiN with the powerful chemisorption of TiO2 well stabilizes S and also alleviates the shuttle effects of polysulfides. This work with simple processes and low cost is expected to promote the further development and application of metal-S batteries.

Multi-step Controllable Catalysis Method for the Defense of Sodium Polysulfide Dissolution in Room-Temperature Na–S Batteries

Room-temperature (RT) sodium-sulfur batteries hold great promise for the development of efficient, low-cost, and environmentally friendly energy storage systems. Nevertheless, the dissolution of long-chain polysulfides is a huge obstacle. In this work, a composite cathode which integrates Ni/Co bimetal nanoparticles as the catalyst and carbon spheres with abundant channels as the host is prepared for RT Na-S batteries. Moreover, a valuable strategy to reduce the dissolution of polysulfides by accurately regulating the two-step reaction kinetics of polysulfide transformation (from Na2S to long-chain polysulfides and then from polysulfides to sulfur) is presented. Through adjusting the ratio of Ni and Co, the optimal cathode with a Ni/Co ratio of 1:2 can retard the first conversion of Na2S to polysulfides and simultaneously accelerate the subsequent transformation of polysulfides to sulfur. In this case, the soluble polysulfides can immediately transform to solid sulfur as soon as it appears, thus avoiding the shuttle of polysulfides. The galvanostatic intermittent titration method and in situ Raman are employed to supervise the transformation of polysulfides during the discharge/charge process. As a result, the composite shows excellent performance as the cathode of RT liquid/quasi-solid-state Na-S batteries in terms of specific capacities, rate capability, and cycle stability.

Approach to Increase the Utilization of Active Material in a High Sulfur-Loaded Cathode for High Areal Capacity Room-Temperature Sodium–Sulfur Batteries

Developing room-temperature sodium–sulfur (RT Na–S) batteries with a high-sulfur-containing cathode and a relatively low amount of electrolyte is the prime factor for implementation of these batter...

Dual-porosity carbon derived from waste bamboo char for room-temperature sodium-sulfur batteries using carbonate-based electrolyte

Room-temperature sodium-sulfur (RT Na-S) batteries have recently drawn a great deal of attention owing to their low cost and high theoretical energy density, making them promising energy storage systems. In this study, a dual-porosity carbon (DPC) matrix with oxygen-containing functional groups derived from waste bamboo char was synthesized by a facile chemical activation for RT Na-S batteries. A high initial discharge capacity of 1168 mAh g−1 at 0.1 C and a superior capacity retention of 320 mAh g−1 at 0.5 C over 600 cycles were obtained. The excellent electrochemical performances came from the unique porous structure and oxygen-containing functional groups of DPC. These properties combined physical and chemical methods to anchor polysulfides and further enhance the electrochemical performance. This study has great significance in terms of building a relationship between waste biomass and electrochemical materials, providing low-cost, green, and sustainable development of advanced energy materials in the future.

Macro-microporous carbon with a three-dimensional channel skeleton derived from waste sunflower seed shells for sustainable room-temperature sodium sulfur batteries

Macro-microporous carbon (MMC), with a three-dimensional channel skeleton and co-doping of heteroatoms derived from waste sunflower seed shells, was synthesized through a facile chemical-activation process. The three-dimensional channel skeleton with a macroporous structure of the MMC formed an interwoven carbon network that effectively improved the electrical conductivity and facilitated the transfer of Na+ in the cell by allowing the electrolyte to permeate easily. The micropores (<0.7 nm) of the MMC are the main sulfur host and serve to trap the small sulfur molecules (<0.5 nm) within the pores, resulting in excellent electrochemical performance in room-temperature sodium sulfur (RT Na–S) batteries with a carbonate-based electrolyte. The co-doping of heteroatoms (N, O) in the MMC matrix can create an active site that improves the electrical conductivity and builds an interaction with sulfur species to inhibit polysulfide shuttling. The confinement of sulfur through these physical and chemical mechanisms results in a high initial discharge capacity of 1598 mAh g−1 at 0.1 C and a superior capacity retention of 330 mAh g−1 after 510 cycles at 1 C. This study provides an attractive material derived from biomass for low-cost and sustainable RT Na–S batteries.

General Synthesis of Single-Atom Catalysts for Hydrogen Evolution Reactions and Room-Temperature Na-S Batteries.

Herein, we report a comprehensive strategy to synthesize a full range of single-atom metals on carbon matrix, including V, Mn, Fe, Co, Ni, Cu, Ge, Mo, Ru, Rh, Pd, Ag, In, Sn, W, Ir, Pt, Pb, and Bi. The extensive applications of various SACs are manifested via their ability to electro-catalyze typical hydrogen evolution reactions (HER) and conversion reactions in novel room-temperature sodium sulfur batteries (RT-Na-S). The enhanced performances for these electrochemical reactions arisen from the ability of different single active atoms on local structures to tune their electronic configuration. Significantly, the electrocatalytic behaviors of diverse SACs, assisted by density functional theory calculations, are systematically revealed by in situ synchrotron X-ray diffraction and in situ transmission electronic microscopy, providing a strategic library for the general synthesis and extensive applications of SACs in energy conversion and storage.

Sulfur-Biological Carbon for Long-Life Room-Temperature Sodium-Sulfur Battery

Room-temperature sodium-sulfur (RT-Na/S) batteries are gaining much attention particularly in large-scale energy storage due to high theoretical energy density and low cost. However, low conductivity and volume expansion of sulfur, as well as severe shuttle effect of soluble sodium polysulfides largely hamper their practical applications. Herein, we report an architecture of sulfur embedded in biological carbon (SBC) as cathode for RT-Na/S batteries. The SBC with N, P co-doping biological carbon and hierarchically porous structure afford fast electron and ion transportation, as well as good mechanical limitation of volume expansion and shuttle effect, therefore achieving excellent cyclic stability (544.7 mAh · g–1 at current density of 200 mA · g –1 after 984 cycles).

Self-Formed Electronic/Ionic Conductive Fe3 S4 @ S @ 0.9Na3 SbS4 ⋅0.1NaI Composite for High-Performance Room-Temperature All-Solid-State Sodium-Sulfur Battery.

Fe3 S4 @ S @ 0.9Na3 SbS4 ⋅0.1NaI composite cathode is prepared through one-step wet-mechanochemical milling procedure. During milling process, ionic conduction pathway is self-formed in the composite due to the formation of 0.9Na3 SbS4 ⋅0.1NaI electrolyte without further annealing treatment. Meanwhile, the introduction of Fe3 S4 can increase the electronic conductivity of the composite cathode by one order of magnitude and nearly double enhance the ionic conductivities. Besides, the aggregation of sulfur is effectively suppressed in the obtained Fe3 S4 @ S @ 0.9Na3 SbS4 ⋅0.1NaI composite, which will enhance the contact between sulfur and 0.9Na3 SbS4 ⋅0.1NaI electrolyte, leading to a decreased interfacial resistance and improving the electrochemical kinetics of sulfur. Therefore, the resultant all-solid-state sodium-sulfur battery employing Fe3 S4 @ S @ 0.9Na3 SbS4 ⋅0.1NaI composite cathode shows discharge capacity of 808.7 mAh g-1 based on Fe3 S4 @S and a normalized discharge capacity of 1040.5 mAh g-1 for element S at 100 mA g-1 for 30 cycles at room temperature. Moreover, the battery also exhibits excellent cycling stability with a reversible capacity of 410 mAh g-1 at 500 mA g-1 for 50 cycles, and superior rate capability with capacities of 952.4, 796.7, 513.7, and 445.6 mAh g-1 at 50, 100, 200, and 500 mA g-1 , respectively. This facile strategy for sulfur-based composite cathode is attractive for achieving room-temperature sodium-sulfur batteries with superior electrochemical performance.

Multiregion Janus-Featured Cobalt Phosphide-Cobalt Composite for Highly Reversible Room-Temperature Sodium-Sulfur Batteries.

Electrode materials with high conductivity, strong chemisorption, and catalysis toward polysulfides are recognized as key factors for metal-sulfur batteries. Nevertheless, the construction of such functional material is a challenge for room-temperature sodium-sulfur (RT-Na/S) batteries. Herein, a multiregion Janus-featured CoP-Co structure obtained via sequential carbonization-oxidation-phosphidation of heteroseed zeolitic imidazolate frameworks is introduced. The structural virtues include a heterostructure existing in a CoP-Co structure and a conductive network of N-doped porous carbon nanotube hollow cages (NCNHCs), endowing it with superior conductivity in both the short- and long-range and strong polarity toward polysulfides. Thus, the S@CoP-Co/NCNHC cathode exhibits superior electrochemical performance (448 mAh g-1 remained for 700 times cycling under 1 A g-1) and an optimized redox mechanism in polysulfides conversion. Density functional theory calculations present that the CoP-Co structure optimizes bond structure and bandwidth, whereas the pure CoP is lower than the corresponding Fermi level, which could essentially benefit the adsorptive capability and charge transfer from the CoP-Co surface to Na2Sx and therefore improve its affinity to polysulfides.

Sulfur-Rich Molybdenum Sulfide as a Cathode Material for Room Temperature Sodium–Sulfur Batteries

The low cost, abundance, and high capacity of sodium and sulfur make them attractive battery materials. However, formation and migration of polysulfides in sulfur batteries causes rapid capacity fade, limiting battery cycle life. Most strategies to mitigate polysulfide shuttling address migration rather than formation and require complicated or expensive synthetic steps. Here, we introduce an amorphous, sulfur-rich molybdenum sulfide as a sulfur equivalent cathode that is simple and easy to make and shows excellent cycling performance with a specific capacity of 537 mAh g–1 at 50 mA g–1, retaining over 200 mAh g–1 at a rate of 1 A g–1.

Conversion of Co Nanoparticles to CoS in Metal-Organic Framework-Derived Porous Carbon during Cycling Facilitates Na2S Reactivity in a Na-S Battery.

Room-temperature sodium-sulfur batteries have attracted wide interest due to their high energy density and high natural abundance. Polysulfide dissolution and irreversible Na2S conversion are challenges to achieving high battery performance. Herein, we utilize a metal-organic framework-derived Co-containing nitrogen-doped porous carbon (CoNC) as a catalytic sulfur cathode host. A concentrated sodium electrolyte based on sodium bis(fluorosulfonyl)imide, dimethoxyethane, and bis(2,2,2-trifluoroethyl) ether is used to mitigate polysulfide dissolution. We tune the amount of Co present in the CoNC carbon host by acid washing. Significant improvement in reversible sulfur conversion and capacity retention is observed with a higher Co content in CoNC, with 600 mAh g-1 and 77% capacity retention for CoNC and 261 mAh g-1 and 56% capacity retention for acid-washed CoNC at cycle 50 at 80 mAh g-1. Post-mortem X-ray photoelectron spectroscopy, transmission electron microscopy, and selected area electron diffraction suggest that CoS is formed during cycling in place of Co nanoparticles and CoN4 sites. Raman spectroscopy suggests that CoS exhibits a catalytic effect on the oxidation of Na2S. Our findings provide insights into understanding the role Co-based catalysts play in sulfur batteries.

Mesoporous Nitrogen-Doped Carbon Nanospheres as Sulfur Matrix and a Novel Chelate-Modified Separator for High-Performance Room-Temperature Na-S Batteries.

Room-temperature sodium-sulfur (RT/Na-S) batteries are considered among the most promising next-generation energy storage and conversion systems because of the earth-abundant reserves of sodium and sulfur. These batteries also possess the advantages of high theoretical gravimetric capacity, high energy density, and low cost. Herein, highly uniform Fe3+ /polyacrylamide nanospheres (FPNs) are fabricated on a large-scale by a facile, low-cost approach. Subsequently, mesoporous nitrogen-doped carbon nanospheres (PNC-Ns), obtained by carbonizing FPNs, are applied as a sulfur matrix to improve the utilization of sulfur, enhance the overall conductivity of the cathode, and inhibit the shuttling of sodium polysulfides (SPSs). In addition, graphene and FPNs are simultaneously coated onto the side of the separator to form a FPNs-graphene-functionalized separator (FPNs-G/separator); here, the mesoporous FPNs effectively anchor and block the SPSs, while the large specific area graphene sheets eliminate the intrinsic mechanical brittleness of the FPNs and improve the overall conductivity of RT/Na-S batteries. When S/PNC-Ns as a cathode and FPNs-G/separator are assembled into an RT/Na-S battery, it delivers a high discharge capacity (639 mAh g-1 at 0.1 C after 400 cycles), stable cycle life (396 mAh g-1 at 0.5 C after 800 cycles), and good rate performance (228 mAh g-1 at 2 C).