Unraveling cation–anion coupling via classic molecular dynamics and ab initio molecular dynamics simulation: Design rules of organic additives for building fluorinated solid electrolyte interphase layer in zinc-ion batteries

Metallic zinc is a compelling anode material for aqueous zinc‑ion batteries (AZIBs), offering high theoretical capacity, low cost, and intrinsic safety. Nevertheless, uneven Zn plating and parasitic side reactions remain persistent challenges that limit cycle life and energy efficiency. To mitigate these issues, organic additives are widely employed, such as fluorinated anions decomposing to form protective F‑based solid electrolyte interphase (SEI), while organic cations promoting uniform Zn²⁺ solvation and distribution at the electrode interface. Despite extensive study of these species in isolation, the synergistic and competitive interactions between cations and anions have received little attention. Here, we introduce a multi‑scale simulation framework that involves density functional theory (DFT), classical molecular dynamics (MD) and ab initio molecular dynamics (AIMD) to probe both long‑range ion distribution and atomistic interfacial decomposition. Based on these insights, we propose electrolyte additive design rules that account for cation–anion interactions, and further use the ways of experiments to verify these conclusions from simulations. Our work underscores the importance of integrated additive engineering.