Revealing the synergy of single-atom cobalt catalysts with hollow carbon spheres for enhanced lithium–sulfur battery performance

Lithium–sulfur (Li–S) batteries boast a theoretical energy density as high as 2600 Wh·kg⁻¹, positioning them as a highly attractive option for future advanced energy storage systems. Challenges such as slow transformation kinetics and shuttle effects associated with lithium polysulfides (LiPSs) have seriously hindered their practical applications. In this paper, we present a new method for the synthesis of hollow carbon-sphere-supported Co monatomic catalysts (Co–N–C). This new synthesis method achieves pyrolytic coordination using a precursor rich in imide (–RC=N–) polymers. This synthesis method not only improves the adsorbability and catalytic activity of LiPS but also significantly weakens the shuttle effect and generates Co–N–C with superior conductivity, abundant hollow structures, and a high specific surface area, thus efficiently capturing and restricting the movement of LiPS intermediates. The dispersed Co monoatomic catalysts (Co SACs) were anchored to a highly conductive nitrogen-doped carbon framework and exhibited symmetric N-coordination active sites (Co–N₄) to ensure fast redox kinetics of LiPS and Li₂S₂/Li₂S solid-state products. The lithium–sulfur battery with Co–N–C as the sulfur carrier showed excellent discharging capacity of 1146.6 mAh·g⁻¹ at a discharge rate of 0.5 C and maintained excellent performance at a high discharge rate of 2 C. The capacity decay rate in 500 cycles was only 0.086% per cycle, reflecting excellent long-term cycle stability. This study highlights the key role of the synergistic effect between single-atom cobalt catalysts and hollow carbon spheres in enhancing the efficiency of lithium–sulfur (Li–S) batteries. It also provides valuable insights into the construction and fabrication of highly active monatomic catalysts. The catalytic conversion efficiency of lithium polysulfides is significantly enhanced when embedded in hollow carbon architectures, which serves as a critical strategy for optimizing the electrochemical behavior of next-generation Li–S batteries.