Separator Coating on Heated Porous Substrates for Stronger Adhesion
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Solution Overview
Problem
Existing methods for manufacturing separators for electrochemical devices face challenges in achieving adequate adhesive strength of the porous coating layer to both the porous substrate and electrodes while maintaining air permeability and ionic conductivity, particularly when using aqueous polymer binders.
Innovation Solution
A method involving the preparation of a coating slurry with polymer binders and inorganic particles, followed by heating the porous substrate above the glass transition temperature of the polymer binder and applying the slurry to form a porous coating layer with a filmed area where the polymer binder is distributed, ensuring a 25-50 wt% coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a crosslinking catalyst master batch is used during the extrusion process to promote silane-modified polyethylene crosslinking reaction, then crosslinking reaction is enhanced, but resin aggregates are generated and homogeneity of physical properties is lowered
Solution Approach 1:
The patent extracts the crosslinking catalyst application step from the extrusion process. Instead of adding crosslinking catalyst during extrusion, the patent applies crosslinking catalyst after extrusion by coating or immersing the separator in a crosslinking catalyst solution, thereby avoiding resin aggregate formation during extrusion while still achieving crosslinking enhancement.
Solution Approach 2:
The patent performs preliminary crosslinking preparation by first forming the separator with silane-modified polyethylene, then subsequently applying the crosslinking catalyst and performing crosslinking treatment. This staged approach allows controlled crosslinking without disrupting the extrusion homogeneity.
2Productivity
If separator thickness is reduced to achieve smaller battery cell sizes, then energy density is improved, but membrane rupture resistance at high temperature deteriorates
Solution Approach 1:
The patent uses silane-modified polyethylene as a composite material that combines the low-temperature flexibility of polyethylene with crosslinking capability. The crosslinked network structure provides high-temperature mechanical strength and membrane rupture resistance even in thin separators (15 µm or less).
Solution Approach 2:
The patent changes the physical-chemical parameters of polyethylene through silane modification and crosslinking. The crosslinking degree is controlled to achieve optimal balance between flexibility at low temperature and rupture resistance at high temperature, enabling thin separator design with improved safety.
3Productivity
If crosslinking catalyst is applied during extrusion to promote crosslinking, then crosslinking efficiency is improved, but resin aggregates form and quality uniformity deteriorates
Solution Approach 1:
The patent extracts the crosslinking catalyst application from the extrusion process itself. The separator is first extruded without crosslinking catalyst to ensure homogeneous structure, then crosslinking catalyst is applied separately through coating or immersion methods, and crosslinking is performed in a controlled subsequent step.
Solution Approach 2:
The patent segments the manufacturing process into distinct stages: (1) extrusion of silane-modified polyethylene without catalyst, (2) application of crosslinking catalyst solution, and (3) controlled crosslinking treatment. This segmentation ensures quality uniformity during extrusion while maintaining crosslinking efficiency in the subsequent controlled environment.
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 method enhances adhesive strength to both the substrate and electrodes, improving peel strength and maintaining air permeability and ionic conductivity, thereby stabilizing the electrochemical device.
Implementation Method 1
it has gradually come to light by experimentation that high-temperature membrane rupture properties can be exhibited by constructing silane crosslinked sections (a silane crosslinked structure) in a polyolefin separator
Implementation Method 2
heat release due to interior battery short circuiting is inhibited by a shutdown function, in which a separator membrane is closed due to melting at a specific temperature, thereby stopping ion transport and battery reactions
Data Source
Figure 1
AI summary
The present disclosure relates to a method for manufacturing a separator for an electrochemical device, which includes (S1) preparing a coating slurry including a polymer binder, inorganic particles, and a dispersion medium; (S2) heating at least one surface of the porous substrate; and (S3) applying the coating slurry prepared in the step (S1) to at least one surface of the porous substrate heated in the step (S2) to thereby form a porous coating layer, wherein the porous coating layer includes an area, where the polymer binder is filmed, in at least a portion of the surface in contact with the porous substrate.