Synergistic effect of adsorption and electrocatalysis of CoO/NiO heterostructure nanosheet assembled nanocages for high-performance lithium–sulfur batteries

Abstract

The dissolution and sluggish redox kinetics of lithium polysulfides (LiPSs) hinder the practical electrochemical performance of lithium–sulfur (Li–S) batteries. The modification of separators with functional materials plays an important role in improving the electrochemical performance of Li–S batteries. In this work, CoO/NiO heterostructure nanosheet assembled nanocages (CoO/NiO@C-NC) derived from NiCo-LDH with ZIF-67 as the template are synthesized to modify the separator of Li–S batteries. CoO/NiO@C-NC shows strong physical adsorption, chemical interaction, and even superior catalytic activity towards LiPSs due to its high surface area and CoO/NiO heterostructure, thus suppressing the dissolution and accelerating the solid–liquid–solid conversion kinetics of LiPSs. In particular, NiO can promote solid–liquid kinetics, and CoO is more favorable to accelerate the liquid–solid kinetics of LiPSs. With CoO/NiO@C-NC coated on the separator, the electrochemical performance of Li–S batteries is improved significantly due to the synergistic effect of adsorption and electrocatalysis of the CoO/NiO@C-NC. The modified Li–S battery shows a high discharge capacity of 738 mA h g⁻¹ at 3C rate, a low capacity decay rate of 0.075% for 500 cycles at 1C, and an areal capacity of 5.8 mA h cm⁻² with a high sulfur loading of 5.87 mg cm⁻². This work provides a novel method for the preparation of hollow heterostructure materials for high-performance Li–S batteries.