Identification of linear scaling relationships in polysulfide conversion on α-In2Se3-supported single-atom catalysts

Abstract

Developing highly active single-atom catalysts (SACs) for suppressing the shuttle effect and enhancing the kinetics of polysulfide conversion is regarded as an important approach to improve the performance of Li–S batteries. However, the adsorption behaviors of polysulfides and the catalytic properties of host materials remain obscure due to the lack of mechanistic understanding of the structure–performance relationship. Here, we identify that the adsorption energies of polysulfides on 3d transition-metal atoms supported by two-dimensional α-In₂Se₃ with downward polarization (TM@In₂Se₃) are highly correlated with the d-band centers of the TM atoms. Introduction of the TM atoms on the α-In₂Se₃ surface improves the electrical conductivity and meanwhile, significantly enhances the adsorption strength of polysulfides and suppresses the shuttle effect. A mechanistic study of polysulfide conversion on TM@In₂Se₃ shows that the Li₂S₂ dissociation is the potential-determining step with low activation energies, indicating that TM@In₂Se₃ can accelerate the kinetics of polysulfide conversion. Electronic structure analysis shows that the kinetics of the potential-determining step on TM@In₂Se₃ is related to the TM-S interaction in Li₂S₂-adsorbed TM@In₂Se₃. A linear scaling relationship between activation energy and the integrated crystal orbital Hamilton population of TM-S in the potential-determining step on TM@In₂Se₃ is identified. Based on the evaluation of stability, conductivity and activity, we concluded that Ti@In₂Se₃, V@In₂Se₃, and Fe@In₂Se₃ are the promising cathode materials for Li–S batteries. Our findings provide a fundamental understanding of the intrinsic link between the electronic structure and catalytic activity for polysulfide conversion and pave a way for the rational design of SAC-based cathodes for Li–S batteries.