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

Abstract

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 verified 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.

Review—The Importance of Chemical Interactions between Sulfur Host Materials and Lithium Polysulfides for Advanced Lithium-Sulfur Batteries

“…Doping carbon with nitrogen is an alternative method to enhance the chemisorption towards LiPSs without compromising the conductivity. 35 Song et al has introduced a mesoporous N-doped carbon with high surface area (824…”

Graphene quantum dots: structural integrity and oxygen functional groups for high sulfur/sulfide utilization in lithium sulfur batteries

“…The calculation is based on the following reaction: coronene_OH+S n 2 − → (coronene_S n ) − +OH − (n = 1, 2, 4, 6, 8) This model was used to represent the terminal edges of the GQDs, and we attached a hydroxyl group (-OH) to one of the edges of the carbon atoms, 'coronene_OH'. 37 A coronene is a polycyclic aromatic hydrocarbon comprising six peri-fused benzene rings with the chemical formula C 24 H 12. Moreover, the coronene model is composed of small sp 2 clusters and is isolated by sp 3 carbon, which is close to individual GQDs without oxygen functional groups, and it has been previously employed as a reduced model of graphene for quantum calculations in lithium-sulfur battery studies. 37,38 The relative energies calculated by DFT for the reactants and products indicate that replacing the terminal hydroxyl group by a sulfur dianion results in a lower energy state.…”

“…37 A coronene is a polycyclic aromatic hydrocarbon comprising six peri-fused benzene rings with the chemical formula C 24 H 12. Moreover, the coronene model is composed of small sp 2 clusters and is isolated by sp 3 carbon, which is close to individual GQDs without oxygen functional groups, and it has been previously employed as a reduced model of graphene for quantum calculations in lithium-sulfur battery studies. 37,38 The relative energies calculated by DFT for the reactants and products indicate that replacing the terminal hydroxyl group by a sulfur dianion results in a lower energy state. The relative energies are shown in Figure 5, where it is clear that the energies of the product decrease when sulfur dianions are replaced with the terminal hydroxyl group.…”

Nitrogen-doped carbons in Li–S batteries: materials design and electrochemical mechanism

“…Song et al (2014) reported the interaction between nitrogen, oxygen, and sulfur in sulfur cathodes. With the use of X-ray absorption near edge structure spectroscopy (Figure 3), the authors determined that nitrogen-doping enable more sulfur accessible to oxygen functional groups on carbon, which is considered as a key role in sulfur immobilization.…”

“…Oxygen K-edge XANES spectra and (B) molecule simulation of mesoporous nitrogen-doped carbon (MPNC) and MPNC-sulfur nanocomposites (Song et al, 2014). The synthetic strategy relies on two steps: (1) growing N-CNTs or N-CNFs with C and N containing precursor; and (2) creating porous N-CNT or N-CNFs through carbon activation processes.…”