Design of transition metal carbonitrides (MCNs) as promising anchoring and high catalytic performance materials for lithium-sulfur batteries

Abstract

The challenges faced by the application of lithium-sulfur (Li-S) batteries with high specific capacity and high energy density include the shuttle effect, which reduces the rate of sulfur reduction reaction (SRR), the difficulty of decomposition of insoluble Li2S during charging, and poor conductivity during charging and discharging. Herein, the adsorption, catalytic and electrical properties of a new class of two-dimensional transition metal carbonitrides (MCNs) have been systematically investigated as candidate cathodes for Li-S batteries. Density functional theory (DFT) calculations combined with van der Waals (vdW) interaction analysis show that TiCN and VCN can effectively suppress the shuttle effect with different solvents. The analysis of the Gibbs free energy and Li2S decomposition energy barrier of the lithiation process show that TiCN and VCN can significantly accelerate the decomposition of Li2S and sulfur reduction reaction, and improves the battery cycle performance. Moreover, the quantum conductivity (G) and density of state (DOS) of the VCN cathode during the whole charge-discharge process indicate that the electrode always has good conductivity. Based on these advantages, VCN is considered as a potential high-performance cathode material for Li-S batteries. This research has a certain guiding effect on the application of two-dimensional (2D) carbon and nitrogen materials in Li-S batteries.