Modifying the electron structure of an FeCoNiZnCu high-entropy alloy with the introduction of Cu to facilitate the catalytic effect in lithium sulfur batteries

Abstract

Developing highly active catalysts with bidirectionally catalytic activity is regarded as an effective strategy for enhancing redox reaction kinetics in lithium–sulfur (Li–S) batteries to boost cathode performance. High-entropy alloys (HEAs) possess unique characteristics, inheriting the functionalities of each of their components while co-adjusting electronic structures, thus showing great potential in catalyzing the complex redox reactions in the Li–S batteries. In this work, composites of HEA nanoparticle (FeCoNiZnCu)–nitrogen-doped carbon nanotubes (NCNTs) are synthesized with uniformly dispersed HEAs inside the NCNT matrix. The introduction of Cu, which has electronic donation capabilities, enhances the catalytic properties of FeCoNiZnCu by shifting the d band center of Fe, Co, and Ni upwards, while the relatively low d band center of Cu broadens the d band distribution in comparison to FeCoNiZn. Benefitting from these improved catalytic properties, batteries using the FeCoNiZnCu–NCNT-modified separator achieved a better rate performance at 2C with a capacity of 679.7 mA h g⁻¹ and cyclic stability at 1C with a decay rate of 0.072% for 600 cycles. This work provides insights into HEA design for optimizing catalytic effects in the Li–S batteries by selecting appropriate elements and adjusting their d band distributions.