Fluorinated Ionic Liquid Electrolyte for Lithium-Ion Battery Safety
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Solution Overview
Problem
Lithium ion batteries face safety concerns due to the volatility and flammability of carbonate-based organic solvents used in their electrolytes, which can lead to thermal runaway and reduced cycle-life characteristics.
Innovation Solution
A non-aqueous organic solvent mixture is developed, comprising a flame-retardant solvent with a fluorinated cation and a phosphorus-based solvent, along with a carbonate solvent, to create an electrolyte that is low in volatility, self-extinguishing, and provides improved thermal stability and cycle-life performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If carbonate-based organic solvents are used in the electrolyte, then high energy density and discharge voltage are achieved, but safety problems arise due to volatility and flammability
Solution Approach 1:
The patent uses a composite electrolyte system combining ionic liquid (fluorinated cation with anion), phosphorus-based solvent, and cyclic carbonate solvent. This composite approach allows the electrolyte to maintain high energy density while the ionic liquid and phosphorus components provide flame retardancy and thermal stability, resolving the contradiction between energy density and safety.
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolyte by introducing fluorinated cations with specific structures (Chemical Formulae 3-4) and phosphorus-based solvents. These parameter changes modify the physical and chemical properties of the electrolyte, reducing flammability while maintaining electrochemical performance and energy density.
2Power
If carbonate-based organic solvents are used in the electrolyte, then high discharge voltage is achieved, but thermal stability deteriorates leading to thermal runaway
Solution Approach 1:
The composite electrolyte system combines ionic liquid, phosphorus-based solvent, and cyclic carbonate solvent in specific proportions. The ionic liquid and phosphorus components act as thermal stabilizers that prevent thermal runaway, while the cyclic carbonate maintains high discharge voltage, thus resolving the contradiction between power and thermal stability.
Solution Approach 2:
The ionic liquid and phosphorus-based solvent components serve as preliminary protective agents that prevent thermal runaway before it occurs. They form stable structures and reduce volatility in advance, counteracting the thermal instability inherent in carbonate-based solvents while maintaining high discharge voltage.
3Productivity
If conventional electrolyte compositions are used, then good charge-discharge performance is achieved, but cycle-life characteristics are reduced
Solution Approach 1:
The patent optimizes the compositional parameters of the electrolyte by specifying precise proportions of ionic liquid (1-40 vol%), phosphorus-based solvent (1-25 vol%), and cyclic carbonate solvent (40-85 vol%). These parameter optimizations enhance both charge-discharge performance and cycle-life by balancing conductivity, stability, and reactivity.
Solution Approach 2:
The composite electrolyte system provides synergistic effects where the ionic liquid enhances stability for longer cycle-life, the phosphorus-based solvent improves thermal resistance, and the cyclic carbonate maintains good charge-discharge performance. This composite approach resolves the contradiction between productivity and duration.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The electrolyte enhances the lithium ion battery's flame retardancy, high temperature storage characteristics, and cycle-life, while maintaining good high rate charge and discharge capabilities.
Implementation Method 1
The flame-retardant solvent includes an ionic liquid including a fluorinated cation and a phosphorus-based solvent
Implementation Method 2
improved thermal stability and cycle-life performance
Data Source
Figure 1
Figure 2~3
AI summary
A non-aqueous organic mixed solvent for a lithium ion battery electrolyte comprising a flame-retardant solvent comprising (i) an ionic liquid comprising a fluorinated cation and (ii) a phosphorus-based solvent, and a carbonate solvent.