Accelerating polysulfide conversion in Li–S batteries: An operando Raman study of B/P-doped CoNi2S4 spheres

Polysulfide shuttle and sluggish redox kinetics remain the major bottlenecks for practical lithium–sulfur (Li–S) batteries. To tackle these issues, we design B/P co-doped CoNi2S4 (CNS-BP) core–shell microspheres as a bifunctional catalyst. The hollow core–shell architecture accommodates volume changes and enhances polysulfide adsorption. B/P dual-doping introduces abundant polar sites into CoNi2S4, which promotes LiPS conversion and improves electrochemical kinetics. As a result, the CNS-BP-S cathode delivers a reversible capacity of 458.7 mAh g−1 after 550 cycles at 2.0 C, with a low capacity decay rate of 0.058% per cycle. To gain deeper insight into the reaction mechanism, we employed in situ Raman spectroscopy to monitor polysulfide conversion in real time, which confirmed the effective suppression of the shuttle effect. This study offers a feasible strategy for high-performance bimetallic sulfide cathodes.