Regulating the Li2S deposition by grain boundaries in metal nitrides for stable lithium-sulfur batteries

Abstract

Catalysis is a fundamental solution in suppressing the shuttling of lithium polysulfides (LiPSs), which is essential to the practical applications of lithium-sulfur batteries with high energy density. However, the uncontrollable deposition of electronic and ionic insulative Li2S always passivates the catalyst surface for the continuous LiPS conversion. Herein, we propose an effective method to regulate Li2S deposition to avoid the catalyst surface passivation by introducing grain boundaries (GBs) in the catalyst. Hollow microspheres composed of MoN-Mo2N heterostructure with abundant and highly accessible GBs were prepared as the models. The results show GBs act as the two-dimensional nucleation sites, guiding the fast nucleation and three-dimensional deposition of Li2S around them, avoiding the formation of dense Li2S coating on their surface. Thus, the high capacity Li2S deposition with enhanced conversion kinetics was achieved. The interlayer composed of the above catalyst and carbon nanotube effectively suppresses the shuttling of LiPSs and promotes their fast conversion, leading to a low capacity decay of 0.049% per cycle at 1 C for 800 cycles for the assembled battery. With a higher sulfur loading of 4.7 mg cm−2 under 0.5 C, high capacity retention of 77.2% after 200 cycles could also be achieved.