Niobium Diboride Nanoparticles Accelerating Polysulfide Conversion and Directing Li2S Nucleation Enabled High Areal Capacity Lithium-Sulfur Batteries.

Abstract

The shuttle effect of polysulfides and Li2S sluggish nucleation are the major problems hampering the further development of lithium-sulfur batteries. The reasonable design for sulfur host materials with catalytic function has been an effective strategy for promoting polysulfide conversion. Compared with other types of transition metal compounds, transition metal borides with high conductivity and catalytic capability are more suitable as sulfur host materials. Herein, a niobium diboride (NbB2) nanoparticle with abundant and high-efficiency catalytic sites has been synthesized by facile solid-phase reaction. The NbB2 with both high conductivity and catalytic nature could regulate 3D-nucleation and growth of Li2S, decrease the reaction energy barrier, and accelerate the transformation of polysulfides. Thus, the NbB2 cathode could retain a high capacity of 1014 mAh g-1 after 100 cycles. In addition, the high initial specific capacities of 703/609 mAh g-1 are also achieved at 5 C/10 C and could run for 1000/1300 cycles within a low decay rate of 0.057%/0.051%. Even with a high sulfur loading up to 16.5 mg cm-2, an initial areal capacity of 17 mAh cm-2 could be achieved at 0.1 C. This work demonstrates a successful method for enhancing the kinetics of polysulfide conversion and directing Li2S nucleation.