Controllable Chain‐Length for Covalent Sulfur–Carbon Materials Enabling Stable and High‐Capacity Sodium Storage

Abstract

couple high-capacity sulfur positive electrodes with earth-abundant sodium negative electrodes are unsurprisingly considered as a promising candidate. [8][9][10][11] In the process of cycle, the elemental sulfur of the cathode is dissolvated, reduced to form various soluble polysulfides, that is, S x 2− ions and radicals (1 ≤ x ≤ 8), and eventually the insoluble Na 2 S 2 and Na 2 S. [8,10,12] However, the practical applications are seriously hindered by several obstacles, in which the fundamental challenges are originated from the insulating properties of elemental sulfur and sodium sulfides, the volume changes at the cathode on cycling and the dissolution of sodium poly sulfides in the electrolyte. [9,[13][14][15] To date, extensive efforts have been made toward the enhancement of RT-Na/S batteries, including Na 2 S cathodes, [16,17] carbonaceous buffer matrixes, [12,18,19] a class of sodium polysulfides, [20,21] and the functional carbon-coated Nafion separator. [22] These approaches, while are validated to improve the cyclability of the RT Na-S batteries, tend to result in complicated synthetic processes and decreased theoretical capacity. In addition, it was suggested that the polar-polar interaction is a strong chemical interaction between polar sodium polysulfides and polar host materials. [23,24] Although there is no universal conclusion on the exact configuration of the interactions due to the complexity of carbon matrix, their similar effect in suppressing the polysulfide shuttle has also been reported in Li-S battery systems. [25][26][27] Instead of relying on polar-polar interactions, the suitably tailored hosts can bind sodium polysulfides through metal-sulfur bonding. Examples of such materials are sub-stoichiometric metal chalcogenides, MXene phases and metal-organic frameworks (MOFs). [28][29][30][31] In practice, these oxide and sulfide materials are able to bridge sodium polysulfides through both polar-polar Na-S(O) interaction and Lewis acid-base bonding, depending on the exposed facets to some extent. [25,32] However, to simply increase metal and/or binder content only neutralizes the advantageous energy density of the overall cell. Moreover, most of the sulfur-carbon electrode materials are directly prepared using elemental S and various carbon matrixes as started materials through vapor-infiltration or meltinfusion method. [8,10] As a result, the aggregated particles are Room temperature sodium-sulfur batteries have emerged as promising candidate for application in energy storage. However, the electrodes are usually obtained through infusing elemental sulfur into various carbon sources, and the precipitation of insoluble and irreversible sulfide species on the surface of carbon and sodium readily leads to continuous capacity degradation. Here, a novel strategy is demonstrated to prepare a covalent sulfur-carbon complex (SC-BDSA) with high covalent-sulfur concentration (40.1%) that relies on SO 3 H (Benzenedisulfonic acid, BDSA) and SO 4 2− as the sulfur source rather than elemental sulfur. M...

Accurate Control Multiple Active Sites of Carbonaceous Anode for High Performance Sodium Storage: Insights into Capacitive Contribution Mechanism

“…In addition, the specific peak assignments are shown in Table S4 in the Supporting Information. As the related publications, three weak peaks centered at ≈785, 452, and 381 cm −1 can be observed, corresponding to the ring stretching vibrations of long‐chain organosulfides (C–S X –C) and the plane bending of short‐chain organosulfides (S–S, C–S), respectively . The peaks gradually become weaker, even almost disappear in the case of N 0.8 S 0.2 ‐MC with declining of sulfur contents.…”

“…Furthermore, the slope extending to low cutoff voltage owing to the sodium intercalation in carbon layers. With increasing the sulfur content in N 0.8 S 0.2 ‐MC and N 0.5 S 0.5 ‐MC, one pair of invertible redox peaks appears at 1.6/2.4 V, which is attributable to the cleavage and formation of long‐chain sulfur bonds (R–S X –R 3 ≤ X ≤ 4) during the sodiation/desodiation reactions . Subsequently, with organosulfides content further increased to N 0.2 S 0.8 ‐MC and S‐MC, two pairs of invertible redox peaks located at 1.6/2.4 and 1.9/2.0 V can be ascribed to phase transformation between Na X S/long and short‐chain organosulfides (R–S X –R 1 ≤ X ≤ 2), which is in good accordance with the conversion mechanism of room‐temperature Na–S batteries …”

“…Hence, the attentions are gradually diverted to heteroatom doping owing to multiple heteroatom can effectively regulate the physicochemical properties of carbonaceous anodes, including electronegativity, electronic conductivity, and hydrophilicity . Nitrogen is the most commonly investigated heteroatom owing to their significant improvement of conductivity and surface wettability between electrode interface and electrolyte, while sulfur doping especially in amorphous carbon prominently enhances sodium storage capacity due to its considerable faraday behavior . Additionally, sulfur doping can also slightly expand the interlayer distances, which is of great assistance for sodium insertion behavior .…”

Bullet‐like Cu9S5 Hollow Particles Coated with Nitrogen‐Doped Carbon for Sodium‐Ion Batteries

“…Sodium‐ion batteries (SIBs) have been considered as a promising alternative to lithium‐ion batteries for large‐scale energy‐storage application in view of the low‐cost and abundance of sodium . Owing to the large size and sluggish diffusion kinetics of Na + ions, it is a great challenge to explore suitable host materials that can effectively and reversibly accommodate Na + ions . Metal sulfides, such as Co x S, Fe x S, Cu x S, and Sn x S have come to attention in view of their excellent redox reversibility and high capacity for sodium storage .…”

Design and Construction of Sodium Polysulfides Defense System for Room‐Temperature Na–S Battery

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popularization and application of this technology can not only reduce the environmental pollution caused by burning fossil fuels, but also address the issue of the intermittency of green energy resources including wind and solar energy, providing convenience for the life and development of human society. [4][5][6][7] These advantages make the room-temperature Na-S battery have broad application prospects in large-scale power grid equipment.However, there are still some burning questions that need to be solved in room-temperature Na-S battery: first, the active S has poor conductivity, resulting in slow electrochemical reaction kinetics and low utilization. [1][2][3] Recently, room-temperature Na-S batteries have attracted much attention because of their high theoretical specific capacity (1675 mAh g −1 ) and energy density (1274 Wh kg −1 ) as well as abundant Na and S resources in the Earth's crust.

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