Glass Fiber Separator With Polymer Gradient for Dendrite Suppression
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Solution Overview
Problem
Existing separators for alkali metal batteries face challenges in mitigating dendrite formation, enhancing mechanical strength, and ensuring stable solid-electrolyte interphase (SEI) formation, particularly in cylindrical or pouch cells, while maintaining integrity during manufacturing.
Innovation Solution
A porous glass fiber substrate with a concentration gradient of negatively charged polymer nanoparticles, such as PTFE, is used to redistribute ion flux and enhance local electric fields, promoting homogeneous alkali metal deposition and suppressing dendrite growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If surface-modified separators with inorganic materials are used to promote homogeneous Li deposition and regulate ionic transport, then dendrite growth is suppressed, but the inorganic layers are brittle and prone to delamination during manufacturing
Solution Approach 1:
The patent combines organic binder polymers (providing flexibility and adhesion) with inorganic coating materials (providing dendrite suppression and ionic conductivity regulation) to create a composite separator structure. This composite approach allows the separator to simultaneously achieve mechanical integrity and dendrite mitigation functionality, resolving the contradiction between brittleness and protective performance.
Solution Approach 2:
The organic binder polymer acts as an intermediary between the inorganic coating particles and the glass fiber substrate. This intermediary layer ensures strong adhesion of the brittle inorganic materials to the flexible substrate, preventing delamination during manufacturing while maintaining the dendrite-suppressing properties of the inorganic coating.
2Strength
If ceramic materials or polymers are used to functionalize the separator to enhance mechanical strength, then separator strength is improved, but dendrite growth is not mitigated to the desired level
Solution Approach 1:
The patent creates a composite structure combining the mechanical strength of ceramic/polymmer materials with the dendrite-suppressing properties of inorganic coatings. The inorganic coating layer (such as Al2O3, SiO2, or TiO2) provides the necessary dendrite mitigation while the underlying ceramic or polymer substrate maintains structural integrity.
Solution Approach 2:
The inorganic coating is applied as a surface layer on the separator, creating local functional quality at the interface where ionic transport occurs. This allows the bulk separator material to provide mechanical strength while the surface coating provides dendrite suppression, with each layer performing its specialized function.
3Ease of manufacture
If conventional separators are used in cylindrical or pouch battery cells, then battery manufacturing is simplified, but the separator integrity is compromised during the winding process
Solution Approach 1:
The composite separator structure with organic binder and inorganic coating provides both flexibility for winding and structural integrity for maintaining separator integrity. The organic polymer matrix allows the separator to bend and conform during the winding process without cracking, while the inorganic coating remains intact to provide continuous protection.
Solution Approach 2:
The organic binder polymer creates a flexible matrix that allows the separator to be bent and wound without compromising its structural integrity. This flexibility is essential for manufacturing cylindrical and pouch battery cells, while the thin film inorganic coating maintains its protective function throughout the winding process.
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 provides a separator that effectively prevents short-circuiting, enhances mechanical strength, and stabilizes the SEI, leading to improved cycling performance and delayed capacity decay in alkali metal batteries.
Implementation Method 1
evaporating the solvent of the dispersion from the porous glass fiber substrate while the particles migrate towards the second major surface of the porous glass fiber substrate under gravity assisted migration
Implementation Method 2
evaporating the solvent of the dispersion from the porous glass fiber substrate
Implementation Method 3
particles of a negatively charged polymer, wherein the particles are distributed in the porous glass fiber substrate such that a concentration of the particles increases throughout a thickness of the porous glass fiber substrate from the first major surface to the second major surface thereof
Data Source
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AI summary
The present invention relates to a separator for a battery comprising: a porous glass fiber substrate having a first major surface and an opposing second major surface, and particles of a negatively charged polymer, wherein the particles are distributed in the porous glass fiber substrate such that a concentration of the particles increases throughout a thickness of the porous glass fiber substrate from the first major surface to the second major surface thereof. The present invention further relates to a battery comprising said separator and a method for producing said separator.