Lithium Battery Electrolyte Flame Retardancy Ion Conductivity
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving improved performance and safety due to the trade-off between flame retardancy and battery performance, as self-extinguishing materials used to enhance safety can deteriorate battery performance.
Innovation Solution
An electrolyte composition including a lithium salt, a sulfur-containing compound, a fluoroalkyl ether, and a phosphazene compound is used, which improves flame retardancy and ion conductivity while maintaining battery performance by optimizing the flash point and viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If self-extinguishing material is added to the electrolyte to improve flame retardancy, then safety is improved, but battery performance deteriorates
Solution Approach 1:
The patent changes the chemical parameters of the electrolyte by introducing a fluorinated cyclic carbonate compound with specific molecular structure (Formula 1) and controlling its concentration (5-50 vol%). This parameter change achieves improved flame retardancy while maintaining battery performance through optimized chemical composition rather than simply adding conventional flame retardants.
Solution Approach 2:
The patent creates a composite electrolyte system by combining the fluorinated cyclic carbonate compound (Formula 1) with other electrolyte components including chain carbonates and lithium salts. This composite approach allows the fluorinated compound to provide flame retardancy while the other components maintain ionic conductivity and battery performance.
2Temperature
If conventional flame retardants are used to improve safety, then flash point increases, but ion conductivity decreases
Solution Approach 1:
The patent achieves improved flash point (temperature parameter) while maintaining ion conductivity by changing the chemical structure parameter of the electrolyte - specifically using the fluorinated cyclic carbonate compound with Formula 1. The fluorine substitution and cyclic structure provide thermal stability for higher flash point while the molecular design maintains compatibility with lithium ion transport.
Solution Approach 2:
The fluorinated cyclic carbonate compound acts as an intermediary substance that mediates between the conflicting requirements of high flash point and high ion conductivity. It forms a protective interface layer that provides thermal stability without blocking lithium ion transport pathways, thus resolving the contradiction between safety temperature and ionic conductivity.
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 composition enhances the stability and performance of rechargeable lithium batteries by improving flame retardancy, ion conductivity, and cycle-life characteristics without compromising battery rate capability.
Implementation Method 1
The ignition and combustion of the electrolyte may be caused by a radical chain reaction of a gas state. Accordingly, a self-extinguishing material may be added to the electrolyte. The self-extinguishing material reacts with the active radicals (H and •OH) produced by the combustion reaction and suppresses (or reduces) the radical chain reaction
Implementation Method 2
The electrolyte typically includes an organic solvent in which a lithium salt is dissolved
Implementation Method 3
An electrolyte composition including a lithium salt, a sulfur-containing compound, a fluoroalkyl ether, and a phosphazene compound is used, which improves flame retardancy and ion conductivity
Data Source
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AI summary
An electrolyte for a rechargeable lithium battery includes a lithium salt, an organic solvent, and an additive. The organic solvent includes a sulfur-containing compound represented by Chemical Formula 1 and a fluoroalkyl ether, and the additive includes a phosphazene compound represented by Chemical Formula 3. A rechargeable lithium battery including the electrolyte may have improved cycle-life characteristics and safety.