Fluorinated Carboxylic Acid Esters for High-Voltage Li-Ion Batteries
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Solution Overview
Problem
Current lithium ion battery electrolyte solvents, such as linear and cyclic carbonates, decompose at high voltages and pose safety concerns due to low boiling points and flammability, limiting cycling performance, especially at high temperatures and voltages above 4.4 V.
Innovation Solution
Development of electrolyte compositions containing novel fluorine-containing carboxylic acid esters, specifically represented by formulas R1—C(O)O—R2, where R1 and R2 vary, combined with electrolyte salts and co-solvents, to enhance cycling performance at high temperatures and voltages up to 5 V in lithium ion batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional carbonate electrolyte solvents are used, then the electrolyte provides good ionic conductivity and electrochemical performance, but the electrolyte decomposes at high voltages above 4.4 V and exhibits low boiling point with high flammability
Solution Approach 1:
The patent modifies the chemical structure of carbonate electrolyte solvents by introducing fluorine atoms at specific positions (alpha, beta, or gamma positions relative to the carbonyl group). This parameter change in molecular composition increases the electrochemical stability window to above 4.4 V and raises the boiling point, thereby reducing flammability while maintaining ionic conductivity
Solution Approach 2:
The patent creates composite electrolyte formulations by combining fluorinated carbonate esters with other carbonate solvents and additives in specific ratios. This composite approach synergistically improves thermal stability and electrochemical performance while maintaining good ionic conductivity and cycling performance at high voltages
2Temperature
If fluorine-containing carboxylic acid ester electrolyte solvents are used, then the electrolyte can be used in lithium ion batteries having high voltage cathodes, but cycling performance is limited particularly at high temperatures
Solution Approach 1:
The patent optimizes the fluorine substitution pattern in carboxylic acid ester molecules, specifically placing fluorine atoms at different positions (alpha, beta, gamma) relative to the carbonyl group. This parameter optimization enhances the electrolyte's thermal stability and its ability to form stable SEI films at high temperatures, thereby improving cycling performance while maintaining high voltage compatibility
Solution Approach 2:
The patent introduces fluorine atoms at specific local positions within the ester molecule rather than uniform substitution. This localized modification at specific carbon positions selectively enhances thermal stability and high-temperature cycling performance while preserving the electrochemical window for high voltage operation
3Stability of the object's composition
If electrolyte solvents are designed for high voltage operation, then the electrolyte stability improves at high voltages, but the cycling performance at high temperatures deteriorates
Solution Approach 1:
The patent systematically varies the fluorine substitution pattern and position in carbonate ester molecules to simultaneously optimize both electrochemical stability at high voltage and thermal stability for high-temperature cycling. This dual-parameter optimization resolves the trade-off between voltage stability and temperature-dependent cycling performance
Data Source
AI summary
Electrolyte compositions comprising novel fluorine-containing carboxylic acid ester solvents are described. The fluorine-containing carboxylic acid ester solvents are represented by the formula R1—C(O)O—R2, whereinR1 is CH3CH2— and R2 is —CH2CHF2,R1 is CH3— and R2 is —CH2CH2CHF2,R1 is CH3CH2— and R2 is —CH2CH2CHF2,R1 is CHF2CH2CH2— and R2 is —CH2CH3, orR1 is CHF2CH2— and R2 is —CH2CH3.The electrolyte compositions are useful in electrochemical cells, such as lithium ion batteries.