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

Eng, Alex Yong Sheng; Wang, Yong; Nguyen, Dan Thien; Tee, Si Yin; Lim, Carina Yi Jing; Tan, Xian Yi; Ng, Man‐Fai; Xu, Jianwei; Seh, Zhi Wei

doi:10.1021/acs.nanolett.1c01763

Cited by 45 publications

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References 54 publications

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“…[ 31 ] Micropores are promising reservoirs for accommodating small S molecules and retaining polysulfides. [ 32 ] Experiments by Archer and co‐workers showed that when S 8 is confined a carbon with a pore size distribution ranging from 0.6 to 1.8 nm, only insoluble short‐chain polysulfide intermediates are formed. [ 33 ] In hosts that are mesoporous, high‐order polysulfides (Na 2 S 5‐8 ) have been reported as well.…”

Section: Resultsmentioning

confidence: 99%

“…The shape of the CV profiles for both electrodes agree with prior reports for a quasi‐solid‐state mechanism that includes the formation of a protective SEI layer. [ 2,8c,32,38 ] The SEI complements the role of micropores and mesopores in preventing direct contact of the electrolyte solution with the soluble sodium polysulfides intermediates. [ 39 ] After first scan, the cycle 1 cathodic peaks disappear, while two new peaks appear over the following cycles (Figure 3a and Figure S12 (Supporting Information)).…”

Section: Resultsmentioning

confidence: 99%

“…It has been reported to be due to formation of short‐chain sodium polysulfides Na 2 S x (2 ≤ x ≤ 4). [ 8c,32,39a ] The second cathodic peak (termed as R2) centers at 1.22 V for MoC/Mo 2 C@PCNT–S and at 1.08 V for PCNT–S. It is associated with the transformation of Na 2 S 4‐2 to Na 2 S. [ 33,39a ] Given nearly identical S mass loading in both electrodes, the markedly higher total current with MoC/Mo 2 C@PCNT–S signals greater S utilization, an effect that is directly attributable to the presence of the MoC/Mo 2 C electrocatalyst.…”

Section: Resultsmentioning

confidence: 99%

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Molybdenum Carbide Electrocatalyst In Situ Embedded in Porous Nitrogen‐Rich Carbon Nanotubes Promotes Rapid Kinetics in Sodium‐Metal–Sulfur Batteries

et al. 2022

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abundance of sulfur. The lower cost and greater availability of sodium as compared to lithium precursors is spurring the incremental focus on Na-S batteries. The traditional high temperature Na-S batteries operating at 300-350 °C comprise the molten electrodes and the solid inorganic β-alumina electrolyte. This mature design is known to have safety issues and a relatively low theoretical energy 760 W h kg −1 (2Na + 3S → Na 2 S 3 ). [2] Instead, there is a strong incentive to develop room-temperature (RT) Na-S batteries which in principle allow the two-electron reduction of sulfur to Na 2 S, with a higher theoretical energy of 1273 Wh kg −1 and less of a safety concern. [3] In practice, RT Na-S cells are likewise held back by several primary challenges including polysulfide (Na 2 S x , 4 ≤ x ≤ 8) dissolution and crossover in liquid electrolytes. Other concerns are the insulating nature of sulfur (σ e = 5 × 10 −30 S cm −1 ) and associated sluggish sulfur redox kinetics, as well as the large volume expansion (170%) of the cathode on cell discharge. [4] Sodium ions have lower solid-state diffusivity and reactivity with solid S than lithium ions. Consequently the electrochemical redox processes in Na-S are more sluggish than in the Li-S counterpart. [5] For Na-S cells, the galvanostatic plateaus are more sloping and less well-defined, while the charge-discharge voltage hysteresis is This is the first report of molybdenum carbide-based electrocatalyst for sulfur-based sodium-metal batteries. MoC/Mo 2 C is in situ grown on nitrogen-doped carbon nanotubes in parallel with formation of extensive nanoporosity. Sulfur impregnation (50 wt% S) results in unique triphasic architecture termed molybdenum carbide-porous carbon nanotubes host (MoC/Mo 2 C@PCNT-S). Quasi-solid-state phase transformation to Na 2 S is promoted in carbonate electrolyte, with in situ time-resolved Raman, X-ray photoelectron spectroscopy, and optical analyses demonstrating minimal soluble polysulfides. MoC/Mo 2 C@PCNT-S cathodes deliver among the most promising rate performance characteristics in the literature, achieving 987 mAh g −1 at 1 A g −1 , 818 mAh g −1 at 3 A g −1 , and 621 mAh g −1 at 5 A g −1 . The cells deliver superior cycling stability, retaining 650 mAh g −1 after 1000 cycles at 1.5 A g −1 , corresponding to 0.028% capacity decay per cycle. High mass loading cathodes (64 wt% S, 12.7 mg cm −2 ) also show cycling stability. Density functional theory demonstrates that formation energy of Na 2 S x (1 ≤ x ≤ 4) on surface of MoC/Mo 2 C is significantly lowered compared to analogous redox in liquid. Strong binding of Na 2 S x (1 ≤ x ≤ 4) on MoC/Mo 2 C surfaces results from charge transfer between the sulfur and Mo sites on carbides' surface.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Molybdenum Carbide Electrocatalyst In Situ Embedded in Porous Nitrogen‐Rich Carbon Nanotubes Promotes Rapid Kinetics in Sodium‐Metal–Sulfur Batteries

et al. 2022

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“…Metal–organic frameworks (MOFs), most commonly zeolitic imidazolate frameworks (ZIFs), have also been reported as suitable precursors for the microporous carbon (MPC) hosts 53–56 . ZIF‐8, synthesized from zinc nitrate and 2‐methylimidazole, is carbonized at high temperatures to obtain microporous carbon structures (Figure 4A).…”

Section: Short‐chain Sulfur Via Physical Confinementmentioning

confidence: 99%

Quasi‐solid‐state conversion cathode materials for room‐temperature sodium–sulfur batteries

Lim

Seh

2022

Battery Energy

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Room-temperature sodium-sulfur batteries (NaSBs) are promising candidates for next-generation large-scale energy storage solutions. However, the wellknown polysulfide shuttling of soluble long-chain sulfur intermediates still remains a limitation in NaSBs, leading to rapid capacity loss arising from the dissolution of active sulfur into the electrolyte. This problem is effectively circumvented in quasi-solid-state conversion cathodes by elimination of the presence of these soluble intermediates altogether, with only insoluble intermediates formed in the process. Herein, we discuss various cathode materials that undergo quasi-solid-state conversion when cycled in a liquid electrolyte, including chemically bonded short-chain sulfur species, shortchain sulfur via physical confinement, and quasi-solid-state conversion cathodes with long-chain sulfur moieties. We conclude by highlighting the current challenges and possible strategies to improve the mechanistic understanding and cycling performance of NaSBs for practical applications.

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“…The fabrication of these insoluble short-chain sulfur cathodes can be achieved via either of two broad strategies: by physically confining the sulfur in microporous carbon hosts − or through covalent bonding to a composite structure . A myriad of covalently bound sulfur compounds have been investigated, including sulfurized polyacrylonitrile, − sulfur- co -polymers, − and more recently, organosulfur-derived thio-compounds. , Beyond these materials, there has also been emerging interest in amorphous transition metal polysulfides as sulfur cathode candidates. − These amorphous metal polysulfides exhibit distinct electrochemical behavior from their crystalline counterparts, with metal–S bonds formed in the composite reportedly anchoring the sulfur species during cycling. , …”

Section: Introductionmentioning

confidence: 99%

Sulfurized Cyclopentadienyl Nanocomposites for Shuttle-Free Room-Temperature Sodium–Sulfur Batteries

et al. 2021

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A major challenge hindering the practical adoption of room-temperature sodium–sulfur batteries (NaSBs) is polysulfide dissolution and shuttling, which results in irreversible capacity decay and low Coulombic efficiencies. In this work, we demonstrate for the first time NaSBs using a ferrocene-derived amorphous sulfurized cyclopentadienyl composite (SCC) cathode. Polysulfide dissolution is eliminated via covalent bonding between the insoluble short-chain sulfur species and carbon backbone. Control experiments with a metal-free composite analogue determined that the iron species in the SCC does not have a significant role in polysulfide anchoring. Instead, the superior electrochemical performance is attributed to sulfur covalently bonded to carbon and the uniform nanoparticulate morphology of the SCC composite. In the carbonate-based electrolyte, a discharge capacity of 795 mAh g(S) –1 was achieved during early cycling at 0.2 C, and high Coulombic efficiencies close to 100% were maintained with capacity retention of 532 and 442 mAh g(S) –1 after 100 and 200 cycles, respectively.

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

Cited by 45 publications

References 54 publications

Molybdenum Carbide Electrocatalyst In Situ Embedded in Porous Nitrogen‐Rich Carbon Nanotubes Promotes Rapid Kinetics in Sodium‐Metal–Sulfur Batteries

Molybdenum Carbide Electrocatalyst In Situ Embedded in Porous Nitrogen‐Rich Carbon Nanotubes Promotes Rapid Kinetics in Sodium‐Metal–Sulfur Batteries

Quasi‐solid‐state conversion cathode materials for room‐temperature sodium–sulfur batteries

Sulfurized Cyclopentadienyl Nanocomposites for Shuttle-Free Room-Temperature Sodium–Sulfur Batteries

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