Co0.7Fe0.3/Co alloy nanoparticles encapsulated in N-doped carbon polyhedrons as efficient catalysts for advanced lithium-sulfur batteries

Abstract

The widespread adoption of lithium-sulfur (Li–S) batteries is hindered by several critical challenges, including the inherently poor electrical conductivity of sulfur, the sluggish reaction kinetics arising from the complex multi-step conversion process, and the abominable shuttle effect of lithium polysulfides (LiPSs). Herein, Co_0.7Fe_0.3/Co alloy nanoparticles were in-situ constructed and confined within CNTs-grafted N-doped carbon polyhedrons (Co_0.7Fe_0.3/Co@NC-CNT), and utilized as efficient catalysts for Li–S batteries. Impressively, the electronic modulation of the Co_0.7Fe_0.3/Co alloy nanoparticles not only effectively accelerates the sulfur redox reaction, but also acts as a strong adsorbent to effectively inhibit the shuttling of polysulfides. Additionally, the hierarchical porous carbon structure facilitates the electron transfer and ion transport, while the derived carbon shell protects binary active sites of Co_0.7Fe_0.3/Co core from electrolyte corrosion. Benefiting from the abundant bimetallic active sites and the meticulously engineered structure, the Co_0.7Fe_0.3/Co@NC-CNT/S cathode yields a promising specific capacity of 1355.2 mAh g⁻¹ at 0.1C, and outstanding capacity retention of 552.3 mAh g⁻¹ over 500 cycles at 2C (∼67.6 % of initial capacity).