As one important component of sulfur cathodes, the carbon host plays a key role in the electrochemical performance of lithium-sulfur (Li-S) batteries. In this paper, a mesoporous nitrogen-doped carbon (MPNC)-sulfur nanocomposite is reported as a novel cathode for advanced Li-S batteries. The nitrogen doping in the MPNC material can effectively promote chemical adsorption between sulfur atoms and oxygen functional groups on the carbon, as verifi ed by X-ray absorption near edge structure spectroscopy, and the mechanism by which nitrogen enables the behavior is further revealed by density functional theory calculations. Based on the advantages of the porous structure and nitrogen doping, the MPNC-sulfur cathodes show excellent cycling stability (95% retention within 100 cycles) at a high current density of 0.7 mAh cm −2 with a high sulfur loading (4.2 mg S cm −2 ) and a sulfur content (70 wt%). A high areal capacity (≈3.3 mAh cm −2 ) is demonstrated by using the novel cathode, which is crucial for the practical application of Li-S batteries. It is believed that the important role of nitrogen doping promoted chemical adsorption can be extended for development of other high performance carbon-sulfur composite cathodes for Li-S batteries.

Nitrogen-Doped Mesoporous Carbon Promoted Chemical Adsorption of Sulfur and Fabrication of High-Areal-Capacity Sulfur Cathode with Exceptional Cycling Stability for Lithium-Sulfur Batteries

V2O3-decorated carbon nanofibers as a robust interlayer for long-lived, high-performance, room-temperature sodium–sulfur batteries

Porous nitrogen-doped graphene nanofibers comprising metal organic framework-derived hollow and ultrafine layered double metal oxide nanocrystals as high-performance anodes for lithium-ion batteries

Lithium-sulfur batteries (LSBs) have the advantages of high energy density and low cost and are considered promising next-generation energy storage systems, but the shuttle effect and slow sulfur redox kinetics severely limit their practical applications. Herein, MoP quantum dot-modified N,P-doped hollow PPy substrates are adopted as separator modification coatings for LSBs. The MoP quantum dots exhibit excellent chemisorption and catalytic conversion capabilities for polysulfides, while the N,P-doped PPy substrates can provide flexible channels for Li+/electron transport and act as a physical barrier to suppress the shuttle effect. As a result, LSBs assembled with modified separators exhibit excellent rate capability (739 mAh/g at 3 C) and cycle performance (600 mAh/g at 1 C after 600 cycles, 0.052% decay per cycle). Moreover, even under a high sulfur loading of 3.68 mg/cm2, areal capacities of 3.58 and 2.92 mAh/cm2 for the 1st cycle and 110th cycle are achieved. In addition, according to density functional theory calculations, MoP quantum dots have large adsorption energy for S8 and Li2Sn, which further confirms the possibility of lowering the initial nucleation energy barrier of Li2S and helps to improve the kinetics of the subsequent Li2S reaction. This study proposes a novel method for using transition-metal phosphides as catalysts in high-performance LSBs.

MoP Quantum Dot-Modified N,P-Carbon Nanotubes as a Multifunctional Separator Coating for High-Performance Lithium-Sulfur Batteries.

Asymmetric separator integrated with ferroelectric-BaTiO3 and mesoporous-CNT for the reutilization of soluble polysulfide in lithium-sulfur batteries

The introduction of a functional interlayer between the cathode and anode in lithium–sulfur battery (LSB) technology results in significant improvements in electrochemical performance. Here, we developed hierarchically structured porous, conductive, and multifunctional N-doped carbon (N-C) nanofibers comprising homogeneously dispersed vanadium nitride quantum dots and hollow N-C nanocages as functional interlayers for advanced LSBs. The freestanding interlayer contains well-developed long-range channels and numerous interconnected hollow N-C nanocages derived from the metal–organic framework. Furthermore, the presence of a N-C framework and vanadium nitride quantum dots measuring several nanometers improves the redox reaction kinetics and provides numerous chemisorption sites for the effective trapping and reuse of lithium polysulfide. As a result, the assembled Li–S cell employing the unique nanostructured freestanding interlayer exhibits superior rate capability and stable cycling performance (decay rate of 0.02% per cycle at 0.5C) considering the high sulfur content (80 wt%) and loading (ca. 4 mg cm−2) in the sulfur electrodes. Even with an ultra-high sulfur loading of 11.0 mg cm−2, the Li–S cell delivered a stable areal capacity of 5.0 mA h cm−2 after 100 charge–discharge cycles at 0.05C. Thus, the uniquely nanostructured interlayer shows high potential for the development of advanced LSBs utilizing pure sulfur electrodes with realistic battery parameters.

Freestanding interlayers for Li-S batteries: Design and synthesis of hierarchically porous N-doped C nanofibers comprising vanadium nitride quantum dots and MOF-derived hollow N-doped C nanocages

MoO3 nanopowders having an average size of 150 nm as anode materials for lithium ion batteries were synthesized by one-pot spray pyrolysis process. During the spray pyrolysis process, concentration difference in a droplet occurred due to the high flow rate of the carrier gas, which induced hollow intermediate powders. The intermediate hollow powders are composed of MoOx and C, and subsequently they are decomposed into MoO3 nanopowders without C under oxidation atmosphere. When MoO3 nanopowders were used as anode materials, the cell showed reversible discharge capacity of 390 mA h g-1 at a current density of 1.0 A g-1 even after 1,000 cycles. The overwhelming cycle stability of the cell is attributed to the MoO3 nanopowders with 150 nm that act as an effective anode material by shortening the diffusion length of Li ions to the electrode and increasing the contact surface with the electrolyte during cycles.

Do Won Jeong

Papers

Freestanding interlayers for Li-S batteries: Design and synthesis of hierarchically porous N-doped C nanofibers comprising vanadium nitride quantum dots and MOF-derived hollow N-doped C nanocages

MoO3 nanopowders as anodes for lithium-ion batteries prepared by one-pot spray pyrolysis process