Ionic-Liquid-Assisted Synthesis of FeSe-MnSe Heterointerfaces with Abundant Se Vacancies Embedded in N,B Co-Doped Hollow Carbon Microspheres for Accelerating the Sulfur Reduction Reaction.

Currently, extensive research efforts are being devoted to suppressing the shuttle effect of polysulfides. The uncontrollable deposition of insulating Li 2 S onto the surface of sulfur host materials dramatically inhibits the continuous reduction of polysulfides in lithium-sulfur (Li-S) batteries. Herein, N,B co-doped hollow carbon microspheres embedded with dense FeSe-MnSe heterostructures and abundant Se vacancies (FeSe-MnSe/NBC) are rationally designed and synthesized via a facile hydrothermal reaction using ionic liquids as dopants. The introduction of abundant heterostructures subtly guides Li 2 S nucleation and deposition in 3D frameworks, thus avoiding the formation of the Li 2 S passivation layer and allowing for continuous Li + diffusion and subsequent nucleation of Li 2 S. Owing to these beneficial features, Li-S batteries comprising an FeSe-MnSe/NBC electrode exhibit significantly improved performance, including a high initial capacity of 1334 mAh g -1 at 0.2 C and ultralong cycle stability with a low capacity fading rate of 0.029% cycle -1 over 1000 cycles at 1.0 C. Remarkably, the FeSe-MnSe/NBC pouch cell delivers a considerable areal capacity of 3.6 mAh cm -2 at 0.1 C. This study provides valuable insight into heterostructures and Se vacancies for developing practical Li-S batteries.