Electrochemical Separator Coating with Preheated Substrate Adhesion
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Solution Overview
Problem
Conventional methods for manufacturing separators for electrochemical devices face challenges in achieving excellent adhesive strength of the porous coating layer to both the porous substrate and electrodes while maintaining air permeability and ionic conductivity, often resulting in deteriorated performance when using aqueous polymer binders.
Innovation Solution
A method involving the preparation of a coating slurry with a polymer binder and inorganic particles, followed by heating the porous substrate to a temperature above the glass transition temperature of the polymer binder but below the melting point of the substrate, and applying the slurry to form a porous coating layer with a filmed area that provides improved adhesive strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a slurry with oil-based polymer binder is used to form porous coating layer, then adhesive strength to porous substrate and electrodes is improved, but distribution control of polymer binder and inorganic particles becomes difficult
Solution Approach 1:
The patent changes the dispersion medium from oil-based to aqueous, and adjusts the molecular weight and chemical structure of the polymer binder to achieve both good distribution control and adequate adhesive strength. Specifically, it uses water-soluble polymers with controlled molecular weights (10,000-1,000,000 g/mol) and specific functional groups to optimize both parameters simultaneously.
2Strength
If higher temperature and pressure are applied in stacking or pressing process, then adhesive strength of porous coating layer is improved, but air permeability and ionic conductivity deteriorate or porous substrate is damaged
Solution Approach 1:
The patent applies preliminary surface treatment to the porous substrate before applying the coating slurry. The substrate surface is pre-heated to a temperature slightly below the polymer binder's glass transition temperature, which activates the substrate surface and improves adhesion during coating application, eliminating the need for subsequent high-temperature pressing that would damage the porous structure.
3Strength
If polymer binder with higher molecular weight is used, then adhesive strength is improved, but distribution uniformity and processing control become difficult
Solution Approach 1:
The patent optimizes the molecular weight parameter of the polymer binder to a specific range (10,000-1,000,000 g/mol) and introduces chemical structure parameters (functional groups, branching degree) to achieve the desired balance. This parameter optimization enables both high adhesive strength and uniform distribution in the aqueous slurry system.
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 the peel strength and adhesive strength of the separator to electrodes, maintaining the advantages of the porous coating layer while ensuring structural stability and performance of the electrochemical device.
Implementation Method 1
lithium ions can move through the interstitial volume
Implementation Method 2
the polymer binder can impart an adhesive strength to the porous coating layer
Implementation Method 3
heating at least one surface of a porous substrate to a temperature higher than a glass transition temperature of the polymer binder
Data Source
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 a porous substrate; and (S3) applying the coating slurry prepared in the step (S1) to the at least one surface of the porous substrate heated in the step (S2) to 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.