Multi-functional CoS2-N-C porous carbon composite derived from metal-organic frameworks for high performance lithium-sulfur batteries

Abstract

Lithium-sulfur (Li-S) battery is recognized as one of the most promising high-energy-density storage system. However, the poor cycle life and low sulfur utilization originating from the shuttling process involving lithium polysulfide (LiPSs) significantly hinder the practical application of Li-S battery. Various approaches have been introduced to retard the shuttle of LiPSs. Herein, a polar cobalt disulfide embedded in porous nitrogen doped carbon frameworks (CoS2-N-C) is synthesized from a single metal-organic framework ZIF-67. When used as a sulfur host for Li-S battery cathode, the CoS2-N-C frameworks can not only limit the dissolution of LiPSs by chemisorption, but also buffer the volume expansion during cycling. More importantly, the electrochemical reaction kinetics is greatly improved. As a result, the Li-S battery based on the S/CoS2-N-C electrode exhibits a high initial discharge capacity of 1288 mAh g−1 at 0.2 C and a superior long cycle life for 500 cycles with a degradation rate as low as 0.064% per cycle at 1 C rate. Even with a high sulfur loading of 5.25 mg cm−2, the battery still delivers a better cycle performance.