Room-temperature Sodium Sulfur Research Articles

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.

Single-Atom Catalysts for Improved Cathode Performance in Na–S Batteries: A Density Functional Theory (DFT) Study

The room-temperature sodium–sulfur (Na–S) batteries have attracted remarkable attention because of their promise to deliver high-capacity and low-cost earth-abundant sodium and sulfur. However, the...

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...

Materials engineering for adsorption and catalysis in room-temperature Na–S batteries

Room-temperature sodium–sulfur (RT Na–S) batteries combine abundant natural resources, low cost, and outstanding energy density, thus attracting much research attention.

Electrochemical redox kinetic behavior of S8 and Na2Sn (n = 2, 4, 6, 8) on vulcan XC-72R carbon in a flowing-electrolyte system

Many studies have shown that sulfur electrodes in room-temperature sodium–sulfur (RT Na–S) batteries undergo a liquid-phase electrochemical reaction. Moreover, the electrochemical redox kinetic behavior of S8 and sodium polysulfides (Na2S8, Na2S6, Na2S4, and Na2S2) is important in understanding the macroscopic kinetics of sulfur electrodes. In this study, a three-electrode electrochemical test system is built using a two-chamber micro-electrolysis cell with a flowing electrolyte and Nafion membrane. Electrochemical kinetic parameters, such as the onset redox potentials, exchange current densities, reaction orders, and apparent activation energies of the sodium polysulfides during the redox process are obtained from a steady-state polarization curve. The onset redox potentials of S8, Na2S8, Na2S6, Na2S4, and Na2S2 on Vulcan XC-72R carbon are 2.37, 2.23, 2.11, 1.99, and 1.83 V (vs. Na/Na+), respectively. Furthermore, the relationship between the discharge capacity of sodium polysulfides and their onset redox potentials is established. The aforementioned kinetic parameters are vital in elucidating the formation of discharge/charge platforms and sloping regions in an RT Na–S battery. The results of this work provide a basis to further understand the performance of RT Na–S batteries.

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).

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.

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).

Free-Radical Catalysis and Enhancement of the Redox Kinetics for Room-Temperature Sodium–Sulfur Batteries

Room-temperature sodium–sulfur (RT Na–S) batteries offer the potential for inexpensive stationary energy storage at the grid and local level. However, their practical performance remains far from t...

Electrocatalyzing S Cathodes via Multisulfiphilic Sites for Superior Room-Temperature Sodium-Sulfur Batteries.

Room-temperature sodium-sulfur (RT-Na/S) batteries hold great promise for sustainable and cost-effective applications. Nevertheless, it remains a great challenge to achieve high capacity and cycling stability due to the low activity of sulfur and the sluggish conversion kinetics between polysulfide intermediates and sodium sulfide. Herein, an electrocatalyzing S cathode is fabricated, which consists of porous core-shell structure and multisulfiphilic sites. The flexible carbon structure effectively buffers volume changes during cycling and provides enclosed spaces to store S8 with exceptional conductivity. Significantly, the multisulfiphilic sites (ZnS and CoS2) enhance catalysis toward multistep S conversion, which effectively suppresses long-chain polysulfides dissolution and improves the kinetics of short-chain polysulfides. Thus, the obtained S cathodes achieve an enhanced cycling performance (570 mAh g-1 at 0.2 A g-1 over 1000 cycles), decent rate capability (250 mAh g-1 at 1.0 A g-1 over 2000 cycles), and high energy density of 384 Wh kg-1 toward practical applications.

Covalent Encapsulation of Sulfur in a MOF‐Derived S, N‐Doped Porous Carbon Host Realized via the Vapor‐Infiltration Method Results in Enhanced Sodium–Sulfur Battery Performance

AbstractPractical applications of room temperature sodium–sulfur batteries are still inhibited by the poor conductivity and slow reaction kinetics of sulfur, and dissolution of intermediate polysulfides in the commonly used electrolytes. To address these issues, starting from a novel 3D Zn‐based metal–organic framework with 2,5‐thiophenedicarboxylic acid and 1,4‐bis(pyrid‐4‐yl) benzene as ligands, a S, N‐doped porous carbon host with 3D tubular holes for sulfur storage is fabricated. In contrast to the commonly used melt‐diffusion method to confine sulfur physically, a vapor‐infiltration method is utilized to achieve sulfur/carbon composite with covalent bonds, which can join electrochemical reaction without low voltage activation. A polydopamine derived N‐doped carbon layer is further coated on the composite to confine the high‐temperature‐induced gas‐phase sulfur inside the host. S and N dopants increase the polarity of the carbon host to restrict diffusion of sulfur, and its 3D porous structure provides a large storage area for sulfur. As a result, the obtained composite shows outstanding electrochemical performance with 467 mAh g−1 (1262 mAh g−1(sulfur)) at 0.1 A g−1, 270 mAh g−1 (730 mAh g−1(sulfur)) after 1000 cycles at 1 A g−1 and 201 mAh g−1 (543 mAh g−1(sulfur)) at 5.0 A g−1.

Ultrastable Sodium-Sulfur Batteries without Polysulfides Formation Using Slit Ultramicropore Carbon Carrier.

The formation of the soluble polysulfides (Na2Sn, 4 ≤ n ≤ 8) causes poor cycling performance for room temperature sodium–sulfur (RT Na–S) batteries. Moreover, the formation of insoluble polysulfides (Na2Sn, 2 ≤ n < 4) can slow down the reaction kinetics and terminate the discharge reaction before it reaches the final product. In this work, coffee residue derived activated ultramicroporous coffee carbon (ACC) material loading with small sulfur molecules (S2–4) as cathode material for RT Na–S batteries is reported. The first principle calculations indicate the space confinement of the slit ultramicropores can effectively suppress the formation of polysulfides (Na2Sn, 2 ≤ n ≤ 8). Combining with in situ UV/vis spectroscopy measurements, one‐step reaction RT Na–S batteries with Na2S as the only and final discharge product without polysulfides formation are demonstrated. As a result, the ultramicroporous carbon loaded with 40 wt% sulfur delivers a high reversible specific capacity of 1492 mAh g−1 at 0.1 C (1 C = 1675 mA g−1). When cycled at 1 C rate, the carbon–sulfur composite electrode exhibits almost no capacity fading after 2000 cycles with 100% coulombic efficiency, revealing excellent cycling stability and reversibility. The superb cycling stability and rate performance demonstrate ultramicropore confinement can be an effective strategy to develop high performance cathode for RT Na–S batteries.

A Biphasic Interphase Design Enabling High Performance in Room Temperature Sodium-Sulfur Batteries

Summary 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. However, little emphasis has been placed on developing sodium anode interphases that combine high Young’s modulus (stiffness), high critical strain (ductility), and low ionic diffusion barrier for cycling at high rates. Here, we report an artificial biphasic interphase comprising two chemically distinct phases, NaOH and NaNH2, which combines high stiffness and high ductility. In addition, the biphasic interphase exhibits a low diffusion barrier for sodium ions, enabling reversible sodium plating and stripping behavior even at extremely high current densities (up to 50 mA cm−2) in symmetric cell configuration. Stable and reversible cycling of a room temperature sodium-sulfur battery is also demonstrated over 500 cycles.

Vanadium carbide nanoparticles incorporation in carbon nanofibers for room-temperature sodium sulfur batteries: Confining, trapping, and catalyzing

Room-temperature sodium-sulfur (RT Na-S) batteries have aroused extensive interest from researchers owing to the high theoretical volumetric energy density, nontoxicity and low-cost. However, poor conductivity of sulfur and high solubility of polysulfides in electrolyte are two major challenges for the practical application of the RT Na-S batteries. Herein, we report a three dimensional self-supported structure with Vanadium carbide (VC) nanoparticles embeddedin carbon nanofibers for RT Na-S batteries. Finally, the VC-CNFs@S electrode displays a reversible capacity of 379 mAh g−1 after 2000 cycles at 0.5C with a high capacity retention of 96.2%. Such outstanding electrochemical property is ascribed to the “confining – trapping – catalyzing” effect of VC-CNFs structure.

An artificial metal-alloy interphase for high-rate and long-life sodium–sulfur batteries

Room-temperature sodium–sulfur battery is considered to be a promising candidate for next-generation batteries due to its high theoretical energy density (~1274 ​Wh kg−1) and natural abundance of elements. There are however, 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. Solid electrolyte interphases that address all 4 challenges simultaneously to enable high-rate cycling of sodium anodes remain scarce in the literature. Here we report an artificial metal-alloy interphase (MAI) comprising sodium-tin alloy, which was synthesized using a facile solid-vapor reaction of metallic sodium with tin tetrachloride vapors, instead of using typical liquid electrolytes with tin-based additives (solid-liquid reaction). The MAI was found to facilitate reversible deposition of sodium at relatively high current densities (2–7 ​mA ​cm−2), and allows sodium electrodes to cycle stably for over 650 cycles at 2 ​mA ​cm−2 in sodium symmetric cells. Owing to the unique properties of MAI, such as strong electrode adhesion (to accommodate volume change), high ionic conductivity (to minimize overpotential), high Young’s modulus (to suppress dendrite growth), and low electrolyte permeability (to minimize electrolyte reduction), the sodium anode with MAI can endure extended cycling test in sodium–sulfur batteries for over 500 cycles with a high Coulombic efficiency of 99.7%. This solid-vapor chemistry concept to synthesize MAIs can also be generalized to other material systems such as sodium-silicon and sodium-titanium alloys.