Fluorinated Battery Electrolyte for High-Temperature Stability
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Solution Overview
Problem
Lithium secondary batteries face degradation and thermal instability at high temperatures due to the thermal decomposition of PF6- anions, leading to increased resistance and potential heat generation or ignition, which compromises battery performance and safety.
Innovation Solution
An electrolyte for lithium secondary batteries is developed, comprising a lithium salt, a fluorine-based organic solvent, and a fluorine-based compound with a specific structure, which enhances thermal stability and flame retardancy, improving electrode wetting and adhesion while maintaining ion transfer capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiPF6 is used as the lithium salt in the non-aqueous electrolyte, then the battery shows good initial performance, but the battery exhibits poor high-temperature stability and thermal runaway risk increases
Solution Approach 1:
The patent replaces LiPF6 with LiBF4 as the lithium salt, changing the chemical composition parameter to improve thermal stability. LiBF4 has higher thermal decomposition temperature and does not generate harmful PF6- ions that lead to resistance increase and heat generation at high temperatures
Solution Approach 2:
The patent uses a composite electrolyte system combining LiBF4 lithium salt with a specific solvent mixture (cyclic carbonate and chain carbonate in 1:1 to 4:1 volume ratio). This composite approach leverages the complementary properties of different components to achieve both good initial performance and excellent high-temperature stability
2Reliability
If conventional organic solvents are used in the electrolyte, then the electrolyte shows good ion conductivity, but the battery exhibits poor flame retardancy and thermal stability
Solution Approach 1:
The patent changes the chemical composition of the electrolyte by using LiBF4 instead of LiPF6, which fundamentally alters the thermal and electrochemical stability parameters. This parameter change eliminates the source of thermal decomposition and heat generation while maintaining ion conductivity
Solution Approach 2:
The patent converts the potential harm of using conventional electrolytes by selecting LiBF4 and optimized solvent ratios that transform the electrolyte into a thermally stable system. The harmful thermal decomposition is converted into beneficial high-temperature stability and flame retardancy
3Reliability
If the electrolyte composition is optimized for thermal stability, then high-temperature life characteristics improve, but electrode wetting and adhesion may be affected
Solution Approach 1:
The patent optimizes the volume ratio parameters of cyclic carbonate to chain carbonate (1:1 to 4:1) to achieve the balance between thermal stability and electrode wetting. This parameter optimization ensures that the electrolyte maintains appropriate viscosity and surface tension for good electrode contact while preserving high-temperature stability
Solution Approach 2:
The patent employs a composite solvent system combining cyclic carbonate (EC, PC) and chain carbonate (DMC, DEC) in specific ratios. This composite approach allows the electrolyte to exhibit both high dielectric constant for ion dissociation and low viscosity for electrode penetration, achieving simultaneous optimization of thermal stability and wetting properties
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 effectively suppresses heat generation and ignition, providing excellent high-temperature life characteristics and stability, with improved electrode adhesion and wetting, thus enhancing the overall performance and safety of lithium secondary batteries.
Implementation Method 1
since the electrolyte according to the present invention uses the fluorine-based solvent and a fluorine-based compound having a specific structure together, surface tension of the electrolyte is reduced, and, as a result, there is an effect of improving electrode wetting and adhesion to an electrode
Implementation Method 2
Since an electrolyte according to the present invention may suppress heat generation/ignition in a battery by using a fluorine-based solvent with excellent flame retardancy, thermal stability is excellent
Implementation Method 3
a non-aqueous electrolyte that becomes a medium for transferring the lithium ions
Data Source
AI summary
The present invention relates to an electrolyte for a lithium secondary battery, which includes a lithium salt, a non-aqueous solvent containing a fluorine-based organic solvent, and a fluorine-based compound represented by [Formula 1], and a lithium secondary battery including the same.