An effective sulfur conversion catalyst based on MnCo2O4.5 modified graphitized carbon nitride nanosheets for high-performance Li–S batteries

Abstract

Lithium–sulfur (Li–S) batteries promise high theoretical specific energy density (2600 W h kg⁻¹), low cost and eco-friendliness. However, their practical development is limited by the shuttle of lithium polysulfides (LiPSs) and sluggish reaction kinetics. Herein, we develop a sulfur conversion catalyst based on MnCo₂O_4.5 modified graphitized carbon nitride nanosheets (CNMCO) to enhance the LiPS immobilization and redox conversion for Li–S batteries. Benefiting from its dense nano-lamellar structure and polar surface, CNMCO synergistically serves as a physical impediment and allows chemical entrapment for LiPSs. In addition, CNMCO exhibits a high electrocatalytic activity towards LiPS conversion as well as Li₂S nucleation and decomposition, which were revealed by cyclic voltammetry and density functional theory calculations. As a consequence, the cell with the multi-functional CNMCO/PP separator exhibits substantially improved electrochemical performance, achieving an enhanced rate capability of ∼600 mA h g⁻¹ at 4C, and an outstanding cycling stability with a low capacity fading rate of 0.032% per cycle for 500 cycles at 2C. This work reports an effective strategy to achieve the immobilization of LiPSs and effective catalytic redox conversion for high-performance Li–S batteries.