Encapsulation of sulfur in MoS2-modified metal-organic framework-derived N, O-codoped carbon host for sodium–sulfur batteries.

The interaction between heteroatom-doped carbon and MoS 2 was deeply analyzed via experiments and theoretical calculations. Compared with N -doped carbon@MoS 2 /S, the N, O-codoped carbon@MoS 2 /S cathode exhibits higher cycle capacity, rate performance, and D N a + . Based on density functional theory (DFT) calculations, the electron transfer from MoS 2 to O-doped carbon was observed owing to the high electronegativity of O, thus increasing the Lewis acidity of MoS 2 and improving its catalytic activity towards NaPSs by weakening the sodium-sulfur bonds, which suggests NOC@MoS 2 is indeed more suitable for RT Na-S batteries. [Display omitted] • Apply the hierarchical MOF-derived flower-like N, O-codoped carbon@MoS 2 composite for RT Na-S batteries for the first time. • The interaction between N, O-codoped carbon, and MoS 2 was analyzed via experiments and theoretical calculations. • Based on electronic structure calculation, the O doping in the carbon matrix can induce the electron transfer from MoS 2 to the carbon substrate, thus enhancing the Lewis acidity of MoS 2 and increasing the reaction kinetics. Room-temperature sodium–sulfur batteries (RT Na-S) are promising energy storage systems with high energy densities and low costs. Nevertheless, drawbacks, including the limited cycle life and sluggish redox kinetics of sodium polysulfides, hinder their implementation. Herein, a heterostructure of MoS 2 nanosheets coated on a metal–organic framework (MOF)-derived N, O-codoped flower-like carbon matrix (NOC) was designed as a sulfur host for advanced RT Na-S batteries. The NOC@MoS 2 hierarchical host provided a sufficient space to guarantee a high sulfur loading and confinement for the volume expansion of sulfur during the charge/discharge process. According to first-principle calculations, the NOC@MoS 2 composite exhibited metallic conductivity because electronic states crossed the Fermi level, which indicates that the introduction of NOC significantly improved the electronic conductivity of MoS 2. Furthermore, electron transfer from MoS 2 to the O-doped carbon sites was observed owing to the strong electronegativity of O, which can effectively increase the Lewis acidity of MoS 2 and weaken the sodium–sulfur bonds in sodium polysulfides after adsorption on the cathode, leading to reductions in the Na 2 S dissociation energy barrier and Gibbs free energy for the rate-limiting step of the sulfur reduction process. Therefore, with the synthetic effects of MoS 2 and N, O-codoped carbon, the obtained cathode exhibited a superior electrochemical performance. [ABSTRACT FROM AUTHOR]