Crosslinked DPVDF Separator Coating for Thermal-Stable Li-Ion Cells
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Solution Overview
Problem
Lithium-ion secondary battery separators face challenges with poor thermal stability and limited electrochemical performance, leading to safety concerns and inefficiencies in charge-discharge processes due to the limitations of polyolefin-based materials, which are not adequately addressed by existing fluorine-based polymers like PVDF and PVDF-HFP.
Innovation Solution
A separator for lithium-ion batteries is developed using polyvinylidene fluoride (DPVDF) through dip coating and crosslinking, where DPVDF is synthesized by dehydrochlorinating P(VDF-CTFE, and applied to polyethylene or polypropylene substrates, with specific coating concentrations and pore structures to enhance thermal stability and electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polyolefin-based separators are used, then manufacturing ease and cost are improved, but thermal stability and electrochemical performance deteriorate
Solution Approach 1:
The patent applies composite materials by combining polyolefin base material with fluorine-based polymer coatings (PVDF, PVDF-HFP). This creates a multi-layer structure where the polyolefin provides mechanical strength and ease of manufacture, while the fluorine-based coating layer provides enhanced thermal stability and electrochemical performance. The composite structure resolves the contradiction by integrating the advantages of both material systems.
Solution Approach 2:
The patent changes the chemical composition parameters of the separator by introducing fluorine-based polymers with specific properties (high dielectric constant, excellent thermal stability). By adjusting the coating concentration and performing crosslinking reactions, the separator's thermal and electrochemical parameters are optimized while maintaining the base polyolefin's manufacturing advantages.
2Reliability
If fluorine-based polymers like PVDF and PVDF-HFP are used for dip coating, then thermal stability and electrochemical performance are improved, but surface morphology control and further modification difficulty worsen
Solution Approach 1:
The patent performs preliminary action by conducting crosslinking reactions of the fluorine-based polymer coating before final separator assembly. This pre-crosslinking step creates a stable, adherent coating layer that maintains surface morphology while providing the desired thermal stability. The crosslinked structure prevents further unwanted modifications and stabilizes the surface properties.
Solution Approach 2:
The patent changes the chemical structure of the fluorine-based polymer by introducing crosslinking bonds through chemical modification. This transforms the linear polymer chains into a three-dimensional network structure, which improves thermal stability and electrochemical performance while maintaining controllable surface morphology through optimized coating parameters.
3Reliability
If DPVDF is applied through dip coating and crosslinking, then thermal stability and ion conductivity are improved, but manufacturing complexity increases
Solution Approach 1:
The patent utilizes porous materials by maintaining the porous structure of the polyolefin base material and ensuring the fluorine-based polymer coating does not block the pores. The crosslinked DPVDF coating is applied in a manner that preserves pore openness, allowing lithium ion transport while providing thermal stability. This approach adds minimal manufacturing complexity while achieving the desired performance improvements.
Solution Approach 2:
The patent uses an intermediary approach by applying the fluorine-based polymer as a thin coating layer on the polyolefin substrate. This intermediate layer provides the necessary thermal and electrochemical properties without requiring complete replacement of the base material, thus limiting the increase in manufacturing complexity to just the coating and crosslinking steps.
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 DPVDF-coated and crosslinked separator exhibits improved thermal stability, increased ion conductivity, and superior charge-discharge performance, maintaining surface morphology and electrolyte affinity, thereby enhancing the safety and efficiency of lithium-ion batteries.
Implementation Method 1
DPVDF is dip-coated on the separator and crosslinked
Implementation Method 2
DPVDF is dip-coated on the separator and crosslinked
Implementation Method 3
DPVDF, which is a polymer compound synthesized by dehydrochlorination of PVDF
Implementation Method 4
providing a path for lithium ions to diffuse between the two electrodes
Data Source
AI summary
A separator for lithium-ion secondary batteries is characterized in that DPVDF is dip-coated on the separator and crosslinked. A material of the separator is selected from polyethylene (PE), polypropylene (PP), cellulose acetate (CA), polyvinylidene fluoride (PVDF), polyethersulfone (PES), or polyethylene terephthalate (PET). A method for manufacturing the separator includes: synthesizing polyvinylidene fluoride (DPVDF) including a double bond by dehydrochlorinating poly(vinylidene fluoride-co-chlorotrifluoroethylene [P(VDF-CTFE)]; coating a separator by dipping in a dipping solution formed by dissolving the DPVDF in an organic solvent; and crosslinking the DPVDF coated on the separator by performing a radical reaction by heat treatment.