Theoretical Design Of Fluorinated Carbonate Solvents And Theoretical Study On Its Solvation Performance

As the national strategy shifts towards low-carbon and environmentally-friendly initiatives,lithium-ion batteries are playing an increasingly important role in the fields of new electronic products and electric new energy vehicles.This article introduces the current state of research on key areas such as the anode,electrolyte,and electrolyte additives of lithium-ion batteries.Of particular emphasis is the role of fluorinated solvents and fluorinated carbonates as electrolyte additives,which enhance the stability,elasticity,and cathode oxidation stability of the electrolyte interface,while also suppressing the decomposition of electrolyte solvents,thus improving the electrochemical performance and coulombic efficiency.Therefore,designing fluorinated carbonate co-solvents or additives is one successful method for improving the performance of common electrolytes.The main focus of this article is to further explore the role of fluorinated carbonates in order to improve the performance of lithium-ion batteries.The research aims to investigate the effect of adding fluorinated carbonates as electrolyte solvent additives on the performance of lithium-ion batteries and address two current issues.To achieve this,the research is divided into two directions: firstly,exploring the chemical space of common carbonate-based solvents through quantum chemical calculations and studying the effect of fluorine substitution on carbonate properties,establishing correlations between the fluorinated structure-electronic structure and property-solvent properties to guide the design of fluorinated carbonate solvent additives;secondly,studying the micro-mechanism of lithium salt dissolution in fluorinated carbonate solutions,particularly how fluorinated carbonate solvents promote anion entry into the lithium ion solvation shell,providing guidance for the development of solvent additives.This research employs methods such as quantum chemical calculations and molecular simulations to calculate relevant properties at the microscopic level,predict electrochemical behavior,and guide practice and improve theoretical levels.Quantum chemical calculations show that fluorination at different positions has different effects.Fluorination at the alpha position affects the oxidation and reduction properties and is suitable for regulating the anode surface reaction and enhancing high-pressure operating stability,while fluorination at the beta position has a better weak solvation effect.Through enhanced sampling of ab initio molecular dynamics simulations,the free energy landscape of the weak solvation additive of fluorinated carbonates on lithium ion solvation structure changes is reconstructed.The free energy changes indicate that fluorinated carbonates can make it easier for anions to enter the lithium solvation layer,which is extremely advantageous for battery performance.This article provides guidance for the design of fluorinated carbonates from a theoretical computational perspective and provides new interpretations of fluorinated carbonate solvation properties.