Balancing Adsorption, Catalysis, and Desorption in Cathode Catalyst For Li–S Batteries

Abstract

AbstractThe complicated electrochemical catalytic conversion process of polysulfides in metal–sulfur batteries involves three steps: adsorption, catalysis, and desorption process. Even as huge efforts are made for the understanding of the separate steps (especially for the adsorption and catalysis process), research focusing on the entire process is still scarce. Herein, a series of cobalt phosphides (CoP, CoP2, and CoP3) is employed with identical hollow morphology as model electrocatalysts to investigate the significance of the desorption process and discuss the balancing among the adsorption, catalysis, and desorption of lithium polysulfides (LiPSs). The experimental data demonstrate that, compared to CoP and CoP3, CoP2 exhibits moderate adsorption of LiPSs, which enhances the reduction kinetics of S8 to Li2S and regulates the desorption of short‐chain LiPSs. Theoretical calculations further confirm that CoP2 with moderate adsorption of LiPSs exhibits better redox kinetics of LiPSs compared to CoP and CoP3. Moderate adsorption enables the CoP2‐based sulfur cathode to deliver excellent stability with 86% capacity retention (2.6 and 2.0 times higher than CoP and CoP3, respectively) over 1000 cycles at 1 C. All these results indicate that in the adsorption‐catalysis‐desorption chain for LiPSs, all steps need to be considered rather than just focusing on one step of the process.