Zn2+–Modulated bimetallic carbides synergized with macro-mesoporous N-rich carbon enabling accelerated polysulfides conversion for high-performance Li-S batteries

Abstract

• Zn 2+ modulated Co 3 ZnC-based catalysts are constructed via a one-pot approach. • Zn 2+ could regulate the valence states of the cobalt active sites. • Co 3 ZnC@NC interlayer can promote the adsorption and redox kinetic of polysulfides. • Co 3 ZnC@NC contributes to superb cycling capacities and high-rate performance. Metal cations could serve as the active sites to adsorb lithium polysulfides (LiPSs) and catalyze the associated multi-electrons redox reactions. Valence modulating/engineering of the metal active centers is an underlying tactic to expedite the sluggish kinetics of LiPSs for high performance lithium-sulfur (Li-S) batteries. Herein, we craft Zn 2+ -modulated bimetallic carbides electrocatalyst of Co 3 ZnC-embedded carbon submicrospheres anchoring on 3D macro-mesoporous N-doped carbon (denoted as Co 3 ZnC@NC) via a facile one-pot synthesis that employs dicyandiamide as the carbon/nitrogen precursor. Results demonstrate that the balance of the predominantly active Co 2+ /Co 0 pair can be effectively modulated by the incorporated zinc cations, which leads to inhibited shuttle effect and accelerates the catalytic conversion kinetics of LiPS intermediates. When acted as the interlayer to modify commercial separator, Co 3 ZnC@NC confers the superb cycling stability on corresponding Li-S batteries with high discharge capacities and exceptionally high-rate performance, owing to the well-defined surface structure and the increased Co 2+ active sites of Co 3 ZnC@NC. Even the sulfur loading is kept at 4 mg cm −2 , the battery achieves an areal capacity of 3.22 mAh cm −2 after 50 cycles. This work unveils the potential of cation modulated bimetal-based electrocatalysts and also inspires an alternative avenue to exploit surface-mediated redox electrocatalysts for high-performance Li-S batteries.