Triphasic Interface Engineering with Metallic Sn/N, B Co-Doped Carbon Matrix for Boosting Reaction Kinetics and Cycling Stability in Lithium-Sulfur Batteries.

Abstract

Lithium-sulfur batteries undergo solid-liquid-solid phase transitions based on a dissolution-deposition reaction mechanism. To effectively suppress the shuttling of soluble polysulfides, catalysts should be incorporated into the cathode to enhance both the adsorption and conversion processes. The formation of a triphasic interface among the catalyst, conductive material, and electrolyte plays a key role in facilitating these reactions. In this study, a composite catalyst (Sn@NBGNs-CNTs), consisting of metallic tin microparticles anchored on nitrogen and boron co-doped graphene nanosheets and partially exfoliated carbon nanotubes, is synthesized as a sulfur host via a simple method. This structure effectively anchors polysulfides at the interface and provided abundant active sites to accelerate redox reaction kinetihcs. As a result, it facilitated charge transfer and polysulfide transport at the interface, leading to an increase in the nucleation-growth rate constants of Li₂S as determined using the critical deposition voltage from the potentiostatic intermittent titration technique. Consequently, the electrode exhibits excellent cycling stability, retaining 93% of its initial capacity after 350 cycles at 1 C with an extremely low-capacity decay rate of 0.003% per cycle.