Bimetallic ZnSe–SnSe2 heterostructure functionalized separator for high-rate Li–S batteries†

Abstract

Lithium polysulfide (LiPS) shuttling is still the core issue in advancing Li–S battery technologies towards high-power and fast-charging commercialized application. In this work, we demonstrate a confined catalysis of LiPSs by a functionalized separator to suppress shuttling and to improve the high rate capability and cycling stability. An oxygenated carbon nitride (OCN)-supported ZnSe–SnSe₂ heterostructure (ZnSe–SnSe₂@OCN) was designed for the functionalized separator. The ZnSe–SnSe₂@OCN functionalized separator gives a high specific capacity of 609 mA h g⁻¹ at 5 C, favorable cycling stability of 350 cycles at 1 C with a decay rate of 0.11% and coulombic efficiency of 98.6%. It also produces low voltage hysteresis (∼17 mV) after 600 h of cycling without significant voltage fluctuations in a Li|Li symmetric cell. The experimental evidence and density functional theory calculations reveal that the bimetallic ZnSe–SnSe₂ sites regulate the density of states at the Fermi level and provide Se–Li, Zn–S and Sn–S chemical bonding interface for LiPS adsorption confinement. This work provides a viable functionalized separator solution for future high-rate Li–S batteries.