In-Situ Photoelectron Spectroscopy Investigation of Sulfurization-Induced Sodiophilic Sites with Model Systems of α-sexithiophene and p-sexiphenyl

Uncontrollable sodium dendrite growth results in poor cycling performance and severe safety issues, hindering practical applications of sodium metal batteries (SMBs). To stabilize sodium metal anodes (SMAs), various strategies have been developed including employing anode hosts and electrolyte additives to establish protective layers. Nevertheless, the understanding of interaction mechanisms between protective materials and SMAs is still limited, which is crucial for the rational design of protective materials. In this work, we investigated the interaction mechanism between sodium metal and sulfur-containing functional groups with comparative model systems of α-sexithiophene (6T) and p-sexiphenyl (6P) through in-situ photoelectron spectroscopy investigations and density functional theory (DFT) calculations. Our results show that sodium atoms tend to interact with sulfur atoms and their connected carbon atoms simultaneously as well as the aromatic carbon atoms of the end groups of 6T molecules, while no chemical interaction between Na and 6P molecules is observed. The observed sulfurization-induced sodiophilic sites can shed light on the rational design of sulfur-containing protective materials and the relevant interface engineering to stabilize SMAs.