First-principles investigation of the catalytic mechanism of CeO2/KB composite separator in Li-S batteries

The CeO2/Ketjen Black (KB) composite separator has been shown to effectively reduce the shuttle effect and improve the reaction kinetics of lithium polysulfides (LiPSs) in lithium-sulfur (Li-S) batteries. A thorough investigation has been conducted using the Perdew-Burke-Ernzehof plus Hubbard U (PBE + U) calculations implemented within the Vienna ab initio simulation package (VASP). The focus has been on the catalytic mechanism of the separator, particularly the migration behavior of LiPSs and the conversion mechanism of Li2S2 -> Li2S on CeO2 and KB surfaces. The study revealed that LiPSs have a strong preference for the CeO2 surface due to more potent adsorption energies. Moreover, it has been discovered that the subsequent migration and conversion processes of LiPSs are governed by the synergistic catalytic effect between CeO2 and KB. The rate-determining step in the overall catalytic process is the migration of Li2S2 on CeO2. These findings provide a deeper understanding of the catalytic mechanism and migration behavior of LiPSs, potentially guiding the development of advanced composite materials for Li-S batteries and facilitating the use of rare earth metal oxides for high energy storage and extended battery life.