Dual-Layer Battery Separator Coating for Adhesion and Porosity
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Solution Overview
Problem
Secondary battery separators face issues with insufficient adhesion to electrodes due to material properties, leading to potential separation and safety risks, particularly in high-temperature conditions, and existing solutions like vapor-induced phase separation methods are difficult to control and environmentally unfriendly.
Innovation Solution
A separator for secondary batteries comprising a porous polymer substrate with a first layer of inorganic particles and a nonparticulate acrylic polymer with a glass transition temperature of 15°C or less, and a second layer of particulate acrylic polymer with a glass transition temperature of 20°C to 50°C, formed by coating a slurry that allows the particulate acrylic polymer to move to the surface, ensuring strong adhesion without clogging pores.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an organic-inorganic composite porous separator comprising inorganic particles and a binder polymer is used to prevent thermal shrinkage, then thermal stability is improved, but interlayer adhesion deteriorates due to material properties causing separator and electrode separation
Solution Approach 1:
The patent changes the physical state parameter of the binder polymer from particulate to non-particulate form. This parameter change enables the binder to form a continuous adhesive layer that effectively bonds the inorganic particles together and to the electrode, resolving the adhesion problem while maintaining the thermal stability provided by the inorganic particles.
Solution Approach 2:
The patent creates a composite coating layer combining inorganic particles (for thermal stability) with a non-particulate binder polymer (for adhesion). This composite structure integrates the beneficial properties of both components: the inorganic particles provide heat resistance while the binder polymer ensures strong interlayer adhesion between the separator and electrode.
2Reliability
If a vapor-induced phase separation method is used to move binder polymer to the separator surface to improve adhesion, then adhesion is improved, but processability deteriorates due to difficulty in humidity control and environmental issues from organic solvent use
Solution Approach 1:
The patent extracts and eliminates the problematic organic solvent from the coating composition, replacing it with an aqueous-based system. This removal of the harmful solvent resolves the environmental issues and simplifies the manufacturing process by eliminating the need for complex humidity control and solvent recovery systems, while still achieving good adhesion through the non-particulate binder polymer.
Solution Approach 2:
The patent uses a simple, environmentally friendly aqueous coating solution that can be applied and dried without complex equipment or extensive processing. The coating formulation is designed to be straightforward and disposable, eliminating the need for expensive solvent recovery systems and complex process control infrastructure required by traditional vapor-induced phase separation methods.
3Ease of manufacture
If binder polymer dissolved in organic solvent is used to coat the separator, then coating is achieved, but porosity deteriorates as the binder polymer penetrates into the pores of the porous polymer substrate
Solution Approach 1:
The patent changes the physical state of the binder polymer from dissolved (in organic solvent) to non-particulate suspended form in an aqueous medium. This parameter change prevents the binder from penetrating into the pores of the porous substrate, as the non-particulate form remains on the surface to form an adhesive layer, thereby maintaining the porosity of the separator while still achieving effective coating.
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 separator achieves good adhesion with electrodes, maintains porosity, and improves safety by preventing thermal shrinkage, while being environmentally friendly and processable, with adhesion strengths of 30 to 200 gf/25 mm and air permeability of 10 to 300 sec/100 cc.
Implementation Method 1
the particulate acrylic polymer (31) moves to the upper part of the inorganic particles (21)
Implementation Method 2
a nonparticulate acrylic polymer (22) having a glass transition temperature of 15°C or less, wherein the nonparticulate acrylic polymer (22) connects and fixes the inorganic particles (21)
Data Source
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AI summary
The present disclosure relates to a separator for a secondary battery comprising a porous polymer substrate; a first layer formed on at least one surface of the porous polymer substrate, and comprising inorganic particles and a nonparticulate acrylic polymer having a glass transition temperature of 15°C or less, wherein the nonparticulate acrylic polymer connects and fixes the inorganic particles; and a second layer formed on a surface of the first layer, and comprising a particulate polymer having a glass transition temperature of 20°C to 50°C. The separator for a secondary battery according to the present disclosure has good adhesion with electrode and can solve the resistance problem in the presence of the inorganic particles.