Interaction Mechanisms Between Nitrogen-Containing Groups and Alkali Metals with Molecular Model System of HATCN

To enable the practical implementation of alkali metal batteries (AMBs), significant endeavors have been focused on enhancing the stability of alkali metal anodes (AMAs) using a range of strategies, such as optimizing electrolyte compositions, constructing anode deposition hosts, and establishing artificial protective layers. Despite significant progress in enhancing battery performance, limited attention has been given to comprehending the interaction mechanisms between alkali metals and protective materials, which is pivotal for the informed development of novel protective materials. Thus, aiming to enhance the comprehension of interaction processes between AMAs and organic protective materials containing various nitrogen groups, we conducted a mechanism study utilizing 1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile (HATCN) as the model material, based on in-situ x-ray and ultraviolet photoelectron spectroscopy (XPS/UPS), and near edge x-ray absorption fine structure (NEXAFS), as well as density functional theory (DFT) calculations. Through the investigation of interaction processes between HATCN and Li/Na, we find that Li or Na interacts with the two different nitrogen-containing groups of HATCN in the same order: preferentially interacts with the inner imine groups of HATCN before interacting with the outer nitrile groups. Interestingly, our findings also reveal that the two distinct nitrogen-containing groups exhibit a smaller difference in their sodiophilicity compared to their difference in lithiophilicity. These valuable insights shed light on the intricate interactions between nitrogen-containing protective materials and AMAs, paving the way for the development of more effective protective materials in the future.