Functional Nitrile Ether Additives for High-Energy-Density Lithium Metal Batteries: Multiscale Mechanism Study on Cyanide Substitution Regulation

As lithium-ion batteries advance toward higher voltages and energy densities, traditional carbonate-based electrolytes not only undergo oxidative decomposition under high pressure but also induce structural degradation of cathode materials and destabilization of the electrode–electrolyte interface (CEI), severely limiting battery cycle life and safety. To address these challenges, this study designed 18 nitrile ether derivatives (EDD series) featuring varying numbers and positions of cyano substituents, using ethylene glycol bis(propionitrile)ether (DENE) as the molecular backbone. A multiscale approach combining density functional theory calculations and molecular dynamics simulations was employed to systematically investigate their performance regulation mechanisms. Theoretical calculations reveal that increasing the number of cyano substituents significantly enhances the redox potential of the molecules. Among these, terminal cyano groups exhibit the most pronounced effect on reducing the reduction potential, while symmetrically distributed cyano substituents are more conducive to broadening the electrochemical stability window. Frontier molecular orbital analysis indicates that cyano substitution primarily lowers the LUMO energy level of the molecules, thereby enhancing their reduction activity. Molecular dynamics simulations further demonstrate that nitrile-ether molecules effectively modulate solvation structures through strong cyanide-Li + coordination, significantly reducing carbonate solvents’ proportion in the primary solvation shell. This regulates lithium ion desolvation processes and transport properties like migration number. Based on a comprehensive evaluation of these multidimensional properties, this study identifies molecule 110011 as a candidate additive suitable for high-voltage cathode interface protection and molecule 102001 as a functional additive prioritized for anode interface film formation. Both exhibit optimal comprehensive performance in terms of interface stability and ion transport efficiency, respectively. This study aims to enhance the electrochemical performance of high-voltage lithium-ion batteries, providing multifaceted theoretical foundations for the rational design of electrolyte additives in high-voltage lithium-ion batteries.