Gel Electrolyte Composition with Controlled Dehydrofluorination
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Solution Overview
Problem
Existing methods for forming gel electrolytes in lithium-ion batteries face challenges in controlling the extent of dehydrofluorination, leading to potential crosslinking side-reactions and limited shelf life, which can affect the performance and stability of the electrolyte.
Innovation Solution
A solution comprising a solvent, a partially unsaturated fluorinated polymer, and an alkali or alkali earth metal salt is used to form a gel electrolyte by evaporation, avoiding the use of bases that can cause crosslinking, and incorporating a specific polymer structure with controlled dehydrofluorination to enhance stability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If base catalysts are used to promote dehydrofluorination of PVDF-HFP, then dehydrofluorination reaction is enhanced, but crosslinking side-reactions occur and shelf life is reduced
Solution Approach 1:
The patent uses an organic acid (acetic acid, propionic acid, or butyric acid) as an intermediary substance to facilitate dehydrofluorination without causing crosslinking. The organic acid acts as a mediator that promotes the desired reaction while avoiding the harmful crosslinking side-reactions associated with base catalysts, thus resolving the contradiction between reaction efficiency and shelf life stability.
Solution Approach 2:
The patent changes the chemical parameter of the catalyst from basic (base catalysts like amines) to acidic (organic acids with pKa values of 4.76, 4.87, or 4.82). This parameter change fundamentally alters the reaction pathway, enabling dehydrofluorination to proceed efficiently while preventing crosslinking side-reactions, thereby maintaining both reaction efficiency and long-term stability.
2Reliability
If extensive dehydrofluorination is achieved, then electrolyte performance is improved, but crosslinking side-reactions increase
Solution Approach 1:
The organic acid serves as a selective intermediary that promotes dehydrofluorination while suppressing crosslinking. By choosing organic acids with specific pKa values (4.76 for acetic acid, 4.87 for propionic acid, or 4.82 for butyric acid), the patent achieves extensive dehydrofluorination necessary for high electrolyte performance without triggering harmful crosslinking side-reactions.
3Productivity
If base catalysts are used for dehydrofluorination, then reaction rate is increased, but mechanical properties of gel electrolyte deteriorate
Solution Approach 1:
The patent changes the catalyst type from base to organic acid, which fundamentally alters the reaction mechanism. This parameter change enables the dehydrofluorination to proceed at high reaction rates while preserving the mechanical integrity of the resulting gel electrolyte, as the acidic pathway avoids the crosslinking that would otherwise compromise mechanical strength.
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 solution results in a gel electrolyte with improved mechanical properties and similar or enhanced electrochemical performance, as evidenced by comparable impedance, lithium transference number, and limiting current density, while maintaining a controlled extent of dehydrofluorination.
Implementation Method 1
A solution comprising a solvent, a partially unsaturated fluorinated polymer, and an alkali or alkali earth metal salt is used to form a gel electrolyte by evaporation
Data Source
AI summary
A solution comprising a solvent, a fluorinated polymer and an alkali or alkali earth metal salt wherein the fluorinated polymer is a partially unsaturated poly(alkylene) polymer.