Rational design of Co9S8/CoO heterostructures with well-defined interfaces for lithium sulfur batteries: A study of synergistic adsorption-electrocatalysis function

The shuttle behavior of soluble lithium polysulfides (LiPSs) and sluggish electrochemical conversion from LiPSs to Li2S lead to poor cycling performance, which is the major problem hindering the practical applications of lithium-sulfur (Li-S) batteries. Herein, we developed a one-pot carbothermal reduction method to synthesize new CoO nanoparticles decorated Co9S8 (Co9S8/CoO) heterostructures with well-defined interfaces, in which CoO shows strong adsorption function and Co9S8 has significant electrocatalysis function. The Co9S8/CoO heterostructures with rationally structural design can not only improve the chemical capturing between CoO and LiPSs but also facilitate the electrocatalytic activity of Co9S8 involving the reaction from soluable LiPSs to insoluble Li2S2 and subsequent solid-solid reaction from Li2S2 to Li2S. The synergistic adsorption-electrocatalysis function is verified by both theoretical calculations and electrochemical characterizations. The Li-S cell with the Co9S8/CoO-Graphene coated separator exhibits a coulombic efficiency of approximately 100% and delivers a specific capacity of 925 mA h g−1 with a fade rate of 0.049% per cycle over 1000 cycles under a high S loading (2.5 mg cm−2). This work provides an emerging view on the design of heterostructures with synergistic adsorption and electrocatalysis function for application in Li-S batteries and catalysis fields.