NiCo (oxy)selenide electrocatalysts via anionic regulation for high-performance lithium–sulfur batteries

Abstract

The sluggish redox kinetics and shuttle effect of polysulfides and difficult oxidation process of Li₂S severely hinder the practical application of Li–S batteries, for which electrocatalysts with highly intrinsic activities are essential to overcome these issues. Anion-regulated electrocatalysts with abundant active sites benefit the redox kinetics by the integration of different anions into the hetero-anionic structure. Herein, a series of NiCo (oxy)selenide electrocatalysts with an oxygen–selenium hetero-anionic structure were designed and fabricated by the introduction of Se²⁻ into NiCo-layered double hydroxide (NiCo-LDH) nanoboxes created by etching cubic ZIF-67 with Ni²⁺. It was demonstrated that the Se-doping NiCo-LDH (NiCo-LDH-Se) electrocatalyst exhibited preferable electrocatalytic activities for sulfur redox reactions. Moreover, the hollow nanobox structures provide a large inner space for sulfur storage, and could effectively suppress the shuttle effect by their chemical binding/adsorption with polysulfide. A fabricated Li–S battery with the NiCo-LDH-Se cathode showed excellent electrochemical performance, revealing stable cycling over 1000 cycles with a low-capacity fading rate of 0.02% per cycle at 2C (1C = 1675 mA g⁻¹) and a high-rate capability (733 mA h g⁻¹ at 4C). This work affords an efficient strategy to accelerate the sulfur reaction kinetics and sheds light on the rational design of high-performance electrocatalysts for Li–S batteries.