Synergistic effect of co-vn-supported nitrogen-doped porous carbon to enhance the catalytic activity and stability of cathode in Lithium–sulfur batteries

Abstract

Transition metal-supported nitrogen-doped carbon materials possess the advantages of high catalytic activity and large specific surface area; therefore, they are considered to be the most promising cathode catalysts for lithium–sulfur batteries. However, their practical application has been impeded by poor rate performance and cycling stability due to sluggish reaction kinetics and the polysulfide shuttling effect. Herein, bimetallic cobalt and vanadium nitride supported on porous nitrogen-doped carbon materials (Co-VN/NC) were prepared in a molten salt medium at high temperatures. The as-prepared Co-VN/NC exhibits a large specific surface area, which provides ample space for loading the metal-based compounds. Furthermore, the bimetallic compounds supported on porous N-doped carbon provide abundant active sites on the surface, which enhance the sulfur-fixing ability while accelerating the conversion of polysulfides. The discharge specific capacity of the Co-VN/NC-based Li-S battery is as high as 1170 mAh g−1 at 0.2 C, and it retains 821 mAh g−1 at 1 C. During cycling stability tests, the average decay rate per cycle is only 0.046% over 400 continuous cycles at 1 C. These electrochemical results demonstrate that the Co-VN/NC is a promising cathode material for practical application in Li–S batteries.