Rose-like NiCo2O4 with Atomic-Scale Controllable Oxygen Vacancies for Modulating Sulfur Redox Kinetics in Lithium-Sulfur Batteries.

Abstract

The long-term stability of Li-S batteries is significantly compromised by the shuttle effect and insulating nature of active substance S, constraining their commercialization. Developing efficient catalysts to mitigate the shuttle effect of lithium polysulfides (LiPSs) is still a challenge. Herein, we designed and synthesized a rose-like cobalt-nickel bimetallic oxide catalyst NiCo2O4-OV enriched with oxygen vacancies (OV) and verified the controllable synthesis of different contents of OV. Introducing the OV proved to be an efficient approach for controlling the electronic structure of the electrocatalyst and managing the absorption/desorption processes on the reactant surface, thereby addressing the challenges posed by the LiPS shuttle effect and sluggish transformation kinetics in Li-S batteries. In addition, we investigated the effect of OV in NiCo2O4 on the adsorption capacity of LiPSs using adsorption experiments and density functional theory (DFT) simulations. With the increase in the level of OV, the binding energy between the two is enhanced, and the adsorption effect is more obvious. NiCo2O4-OV contributes to the decomposition of Li2S and diffusion of Li+ in Li-S batteries, which promotes the kinetic process of the batteries.