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.