Synergistic Effects of Co 3 Se 4 and Ti 2 C 3 T x for Performance Enhancement on Lithium-Sulfur Batteries.

As electronic equipment develops rapidly, higher requirements are placed on electrochemical energy-storage devices. These requirements can be met by a lithium-sulfur (Li-S) battery since it has an impressive energy density of 2600 Wh kg -1 and a high theoretical specific capacity of 1675 mAh g -1 . Pitifully, the sluggish redox reaction kinetics and the shuttle effect of polysulfide seriously limit its applications. Separator modification has been proven to be an effective strategy for improving the performance of Li-S batteries. Herein, we have designed a competent three-dimensional separator. It is obtained by embedding Co 3 Se 4 nanoparticles on nitrogen-doped porous carbon (Co 3 Se 4 @N-C) by high-temperature selenization of ZIF-67, which are compounded with Ti 3 C 2 T x by electrostatic dispersion self-assembly, and the compound is used to adjust the surface properties of a polypropylene (PP) separator. Due to the synergistic effect of the superior catalytic performance of Co 3 Se 4 @N-C and the enhancement of adsorption and conductivity bestowed by Ti 3 C 2 T x , lithium-sulfur batteries perform excellently with the modified PP separator. Specifically, the battery with a Co 3 Se 4 @N-C/Ti 3 C 2 T x -modified PP separator exhibits an outstanding rate performance of 787 mAh g -1 at 4C, and stable performance is maintained after 300 cycles at 2C. The density functional theory (DFT) calculations are also performed to confirm the synergistic effect of Co 3 Se 4 @N-C and Ti 3 C 2 T x . This design integrates the merits of catalysis and adsorption and provides a new method for constructing high-performance lithium-sulfur batteries.