Electrostatic Potential-Induced Co-N4 Active Centers in a 2D Conductive Metal-Organic Framework for High-Performance Lithium-Sulfur Batteries.

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The use of single-atom catalysts is a promising approach to solve the issues of polysulfide shuttle and sluggish conversion chemistry in lithium-sulfur (Li-S) batteries. However, a single-atom catalyst usually contains a low content of active centers because more metal ions lead to generation of aggregation or the formation of nonatomic catalysts. Herein, a 2D conductive metal-organic framework [Co3(HITP)2] with abundant and periodic Co-N4 centers was decorated on carbon fiber paper as a functional interlayer for advanced Li-S batteries. The Co3(HITP)2-decorated interlayer exhibits a chemical anchoring effect and facilitates conversion kinetics, thus effectively restraining the polysulfide shuttle effect. Density functional theory calculations demonstrate that the Co-N4 centers in Co3(HITP)2 feature more intense electron density and more negative electrostatic potential distribution than those in the carbon matrix as the single-atom catalyst, thereby promoting the electrochemical performance due to the lower reaction Gibbs free energies and decomposition energy barriers. As a result, the optimized batteries deliver a high rate capacity of over 400 mA h g-1 at 4 C current and a satisfying capacity decay rate of 0.028% per cycle over 1000 cycles at 1 C. The designed Co3(HITP)2-decorated interlayer was used to prepare one of the most advanced Li-S batteries with excellent performance (reversible capacity of 762 mA h g-1 and 79.6% capacity retention over 500 cycles) under high-temperature conditions, implying its great potential for practical applications.