Polymer Adhesive Separator Coating That Preserves Membrane Porosity
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Solution Overview
Problem
The use of wetting agents in forming a polymer adhesive layer on polyolefin-containing porous membranes for electrochemical devices leads to increased resistance and decreased air permeability due to permeation into the membrane pores during coating and drying.
Innovation Solution
A method involving an aqueous polymer slurry comprising particulate binder polymers with a glass transition temperature (Tg) of 20°C or more and particle size of 300 to 800 nm, and particulate acrylic binder polymers with a Tg of −10°C or less and particle size of 100 to 200 nm, is used to coat and dry on polyolefin-containing porous membranes, with a specific ratio and concentration of these components to prevent wetting agent permeation and enhance adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a wetting agent is added to the aqueous slurry to improve coating on the hydrophobic polyolefin-containing porous membrane, then the coating quality is improved, but the wetting agent permeates into the pores of the membrane causing resistance to rise and air permeability to decrease
Solution Approach 1:
A hydrophilic polymer coating layer is introduced as an intermediary between the hydrophobic polyolefin-containing porous membrane and the aqueous slurry. This intermediate layer improves the wettability of the membrane surface, enabling uniform coating of the aqueous slurry without requiring wetting agents that would permeate into the membrane pores and cause harmful effects.
Solution Approach 2:
The invention applies a hydrophilic polymer coating layer specifically on the surface of the polyolefin-containing porous membrane where the aqueous slurry will be applied. This local modification of surface properties (making the surface hydrophilic while keeping the bulk membrane hydrophobic) enables improved coating quality without affecting the overall pore structure and air permeability of the membrane.
2Manufacturing precision
If the polyolefin-containing porous membrane is made more hydrophilic to improve aqueous slurry coating, then coating uniformity is improved, but the membrane's air permeability and resistance characteristics deteriorate
Solution Approach 1:
The invention applies a hydrophilic polymer coating layer specifically on the surface of the polyolefin-containing porous membrane where the aqueous slurry will be applied. This local modification of surface properties (making the surface hydrophilic while keeping the bulk membrane hydrophobic) enables improved coating uniformity without affecting the overall pore structure and air permeability characteristics of the membrane.
Solution Approach 2:
The membrane system is segmented into two distinct functional layers: the bulk polyolefin-containing porous membrane that provides air permeability and resistance characteristics, and the surface hydrophilic polymer coating layer that provides coating uniformity. This segmentation allows each layer to optimize its specific function without compromising the other.
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
This method results in a separator with reduced resistance and improved air permeability by preventing wetting agent penetration into the membrane pores, while maintaining strong adhesion to the electrode.
Implementation Method 1
coating the aqueous polymer slurry on at least one surface of a polyolefin-containing porous membrane and drying the aqueous polymer slurry
Implementation Method 2
the adhesive layer of binder polymer particles is formed on the surface of the porous membrane
Data Source
AI summary
Disclosed is a method for manufacturing a separator having a polymer adhesive layer. The method includes preparing an aqueous polymer slurry comprising a particulate binder polymer having a glass transition temperature Tg of 20° C. or more and a particle size D50 of 300 to 800 nm, a wetting agent, and a particulate acrylic binder polymer having a glass transition temperature Tg of −10° C. or less and a particle size D50 of 100 to 200 nm, and coating the aqueous polymer slurry on at least one surface of a polyolefin-containing porous membrane having pores and drying the aqueous polymer slurry.