Molecular docking-driven anion coordination enabling SEI engineering for ultrastable all-solid-state lithium metal batteries

Abstract

Regulating lithium (Li) salt decomposition to construct a stable solid electrolyte interphase (SEI) represents a pivotal strategy for mitigating Li dendrite and unlocking the full potential of polymer-based all-solid-state Li metal batteries. However, this approach necessitates precise manipulation of the coordination chemistry and decomposition kinetics of Li-salt anions, which remains a formidable challenge in the field. Herein, we unveil a molecular docking-guided design framework that correlates the molecular topology of ligands with bis(trifluoromethanesulfonyl)imide (TFSI⁻) anion coordination chemistry in poly(ethylene oxide) (PEO)-based solid polymer electrolytes. Theoretical calculations and experimental investigations elucidate that short-chain dithiols (e.g., 1,2-ethanedithiol, C2) exhibit optimal spatial complementarity and superior molecular docking efficacy with TFSI⁻ compared to long-chain analogues. Intermolecular hydrogen bonding redistributes electron density toward TFSI⁻, promoting its decomposition and enhancing LiF content in the SEI, thereby effectively suppressing Li dendrite growth. Consequently, the Li||LiFePO₄ cells equipped with PEO-LiTFSI-C2 electrolyte achieve a remarkable 99.2% capacity retention after 580 cycles at 1.0 C, surpassing both long-chain dithiol systems and most previously reported electrolytes. This work provides mechanistic insights into the anion-coordination-mediated SEI formation process. Furthermore, the molecular docking is expected to play a significant role in understanding and researching the interfacial chemistry of all-solid-state Li metal batteries.