Multiscale Theoretical Study of Cyano-Substitution Strategy on Trimethyl Phosphate for High-Voltage Lithium Metal Batteries

The growing demand for high-energy-density lithium-ion batteries is driving the adoption of high-voltage cathodes and lithium-metal anodes. Recent studies highlight the synergistic role of phosphate and nitrile groups in stabilizing transition-metal cathode interfaces. To leverage this, we employed quantum-chemical calculations and molecular dynamics to design and evaluate a series of cyano-functionalized trimethyl phosphate derivatives as potential electrolyte additives for high-voltage lithium-metal batteries. Multiscale simulations demonstrate that cyano-functionalized trimethyl phosphate derivatives serve as effective interphase modifiers in high-voltage lithium-metal batteries. Introducing cyano groups enhances the oxidation stability while reducing reductive resistance. The electronic effect weakens Li⁺ coordination but strengthens PF₆^- affinity, promoting anion participation in the solvation sheath and facilitating an inorganic-rich interphase formation. Notably, specific molecules form stable seven-membered chelate rings with Li⁺, ensuring their incorporation into the inner solvation structure. Concurrently, most compounds show efficient adsorption toward HF and H₂O, mitigating interfacial corrosion. At the cathode, cyano groups may suppress dissolution under high voltages by chelating transition metals. Building upon these molecular properties, promising high-voltage cathode-stabilizing additives were theoretically screened. Our combined quantum-chemical and molecular-dynamics approach constitutes a broadly applicable framework for the accelerated discovery of an advanced cyano-based electrolyte additive for high-voltage Li-metal batteries.