Fluorination Molecular Engineering of Trimethyl Phosphite: A Multiscale Theoretical Study

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Fluorination is crucial for advancing lithium-ion battery performance, addressing limitations in voltage, lifespan, and safety.
• Trimethyl phosphite (TMPi) is a phosphorus-based electrolyte additive known for flame retardancy and suppressing side reactions, but it lacks sufficient oxidation stability at high voltages.

Purpose of the Study:

• To systematically investigate the effects of fluorination on TMPi's electronic structure and properties for high-voltage lithium-ion battery applications.
• To identify optimal fluorinated TMPi derivatives as electrolyte additives that enhance stability and performance.

Main Methods:

• Theoretical investigation using quantum chemical calculations and molecular dynamics simulations.
• Systematic modification of TMPi through fluorination at varying positions and quantities.
• Analysis of electronic structure, oxidation stability, reduction activity, solvation structure, and ion transport properties.

Main Results:

• Fluorine substitution in TMPi lowers HOMO energy and enhances oxidation stability via electron-withdrawing effects.
• Moderate fluorination improves interphase formation, while increased fluorination optimizes reduction activity and weakens coordination.
• TMPi_133 was identified as the optimal additive, balancing excellent oxidation stability and film-forming capability with unimpeded ion transport.

Conclusions:

• Fluorinated TMPi derivatives offer tunable electronic properties and improved stability for high-voltage lithium-ion batteries.
• The study provides practical design strategies for developing advanced phosphite-based electrolyte additives.
• TMPi_133 demonstrates significant potential as a functional interfacial additive for superior battery performance.