Binary Sulfiphilic Nickel Boride on Boron-Doped Graphene with Beneficial Interfacial Charge for Accelerated Li-S Dynamics.

Abstract

The "shuttle effect" and slow conversion kinetics of lithium polysulfides (LiPSs) are stumbling block for high-energy-density lithium-sulfur batteries (LSBs), which can be effectively evaded by advanced catalytic materials. Transition metal borides possess binary LiPSs interactions sites, aggrandizing the density of chemical anchoring sites. Herein, a novel core-shelled heterostructure consisting of nickel boride nanoparticles on boron-doped graphene (Ni3 B/BG), is synthesized through a graphene spontaneously couple derived spatially confined strategy. The integration of Li2 S precipitation/dissociation experiments and density functional theory computations demonstrate that the favorable interfacial charge state between Ni3 B and BG provides smooth electron/charge transport channel, which promotes the charge transfer between Li2 S4 -Ni3 B/BG and Li2 S-Ni3 B/BG systems. Benefitting from these, the facilitated solid-liquid conversion kinetics of LiPSs and reduced energy barrier of Li2 S decomposition are achieved. Consequently, the LSBs employed the Ni3 B/BG modified PP separator deliver conspicuously improved electrochemical performances with excellent cycling stability (decay of 0.07% per cycle for 600 cycles at 2 C) and remarkable rate capability of 650 mAh g-1 at 10 C. This study provides a facile strategy for transition metal borides and reveals the effect of heterostructure on catalytic and adsorption activity for LiPSs, offering a new viewpoint to apply boride in LSBs.