Boosting Catalytic Activity by Seeding Nanocatalysts onto Interlayers to Inhibit Polysulfide Shuttling in Li-S Batteries

The shuttling of soluble lithium polysulfides (LiPSs) is one of the main bottlenecks to the practical use of Li-S batteries. It is reported that in situ synthesized ultrasmall vanadium nitride nanoparticles dispersed on porous nitrogen-doped graphene (denoted VN@NG) as a catalytic interlayer solves this problem. The ultrasmall size of VN particles provide ample triple-phase interfaces (the reactive interfaces among VN nanocatalyst, NG conductive substrate, and electrolyte) for accelerating LiPS conversion and Li2S deposition, which greatly reduces the accumulation of LiPSs in the electrolyte and therefore inhibits the shuttle effect. Their high catalytic activity is confirmed by a reduced activation energy of the Li2S4 conversion step based on temperature-dependent cyclic voltammetric (CV) measurements and the reduced shuttle effect is detected by in situ Raman spectra. With the VN nanocatalyst, Li-S batteries have an outstanding cycling performance with a low capacity decay rate of 0.075% per cycle over 500 cycles at 2 C. A high capacity retention of 84.5% over 200 cycles at 0.2 C is achieved with a high sulfur loading of 7.3 mg cm(-2).

Automated summary

The use of in situ synthesized ultrasmall vanadium nitride nanoparticles dispersed on porous nitrogen-doped graphene as a catalytic interlayer effectively addresses the shuttle effect caused by soluble lithium polysulfides in Li-S batteries. The ultrasmall size of the vanadium nitride particles provides ample triple-phase interfaces for accelerating LiPS conversion and Li2S deposition, resulting in reduced accumulation of LiPS in the electrolyte and inhibition of the shuttle effect. This approach demonstrates high catalytic activity, as evidenced by a significantly reduced activation energy for Li2S4 conversion and a detected decrease in the shuttle effect, thus leading to outstanding cycling performance and high capacity retention in Li-S batteries.