Adsorption and electrocatalytic properties of polysulfides by Ni-N coordination structures

Abstract

In the field of energy storage, lithium-sulfur batteries are considered a highly promising energy storage technology due to their exceptional theoretical energy density. However, the "shuttle effect" of lithium polysulfides (LiPSs) and the sluggish redox kinetics of the sulfur cathode have hindered their commercialization. Addressing these challenges, this study successfully anchored Ni single atoms on N-Doped Hollow Carbon Spheres (Ni-NHCS) via a one-step impregnation method, fabricating an efficient sulfur carrier material. The Ni single atoms in Ni-NHCS form highly chemically active Ni-N coordination structures with nitrogen atoms, significantly enhancing the chemical adsorption capacity for LiPSs and effectively facilitating their conversion reactions. Experimental results and theoretical calculations both confirm the strong interaction between Ni-NHCS and LiPSs, thereby improving the utilization rate of sulfur and the electrochemical performance of the battery. Moreover, the hollow carbon sphere structure not only enhances the conductivity of sulfur but also effectively suppresses volume expansion during charge-discharge processes. Consequently, lithium-sulfur batteries with Ni-NHCS as the sulfur carrier material exhibit outstanding electrochemical performance, achieving a high specific capacity of 1316 mAh g^-1 at a current density of 0.2 C; even at a high current density of 2 C, it can still provide a stable output of 697 mAh g^-1. More impressively, after 2850 cycles under 2 C conditions, the capacity fade rate is only 0.027 %, demonstrating excellent cyclic stability. By effectively suppressing the "shuttle effect" and optimizing redox kinetics, this study provides a new strategy for enhancing the performance of lithium-sulfur batteries. These findings not only validate the high-efficiency application potential of carbon-supported metal single-atom catalysts in sulfur cathode materials but also offer new insights for advancing lithium-sulfur battery technology and achieving sustainable, efficient energy storage solutions.