Dual-Layer Battery Separator Coating for Adhesion and Thermal Shrinkage
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Solution Overview
Problem
Existing separators for secondary batteries face challenges with adhesion to electrodes in the presence of inorganic particles, leading to potential internal short circuits due to thermal shrinkage and insufficient interlayer adhesion.
Innovation Solution
A separator design featuring a porous polymer substrate with a first layer containing inorganic particles and a nonparticulate acrylic polymer, and a second layer comprising a particulate acrylic polymer with a glass transition temperature of 20° C. to 50° C., enhancing adhesion with electrodes while maintaining air permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an organic-inorganic composite porous separator comprising inorganic particles and a binder polymer is used, then thermal shrinkage resistance is improved, but interlayer adhesion deteriorates
Solution Approach 1:
The patent applies local quality by creating a dual-layer coating structure where the first layer (containing inorganic particles and binder polymer) provides thermal shrinkage resistance, while the second layer (particulate acrylic polymer) provides adhesion to the electrode. Each layer has different properties optimized for its specific function, resolving the contradiction between thermal stability and adhesion.
Solution Approach 2:
The patent uses composite materials by combining inorganic particles with binder polymer in the first layer, and particulate acrylic polymer in the second layer. This composite structure allows the separator to simultaneously achieve thermal shrinkage resistance from the inorganic particles and adhesion from the polymer layers, particularly the particulate acrylic polymer that adheres to the electrode surface.
2Strength
If a vapor-induced phase separation method is used to form an adhesive layer, then adhesion is improved, but processability deteriorates
Solution Approach 1:
The patent applies parameter changes by carefully controlling the glass transition temperature of the particulate acrylic polymer in the second layer (20°C to 50°C). This temperature parameter control allows the polymer to be solid during handling but become pliable during electrode stacking, enabling good adhesion without requiring complex vapor-induced phase separation processes.
3Strength
If the binder polymer content near the separator surface is increased, then adhesion is improved, but pore clogging increases
Solution Approach 1:
The patent applies segmentation by dividing the coating into two distinct layers: the first layer contains the binder polymer mixed with inorganic particles, while the second layer consists of particulate acrylic polymer applied on top. This segmentation allows the binder polymer to be positioned away from the separator surface in the first layer, preventing pore clogging while still providing adhesion through the second layer's particulate polymer that contacts the electrode.
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 proposed separator achieves improved adhesion with electrodes and maintains good air permeability, addressing the issues of internal short circuits and thermal shrinkage, thereby enhancing the safety and performance of secondary batteries.
Implementation Method 1
the nonparticulate acrylic polymer connects and fixes the inorganic particles
Implementation Method 2
the second layer includes a particulate acrylic polymer... enhancing adhesion with electrodes
Data Source
AI summary
A separator for a secondary battery comprising a porous polymer substrate; a first layer on at least one surface of the porous polymer substrate, wherein the first layer includes 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 on an upper surface of the first layer, wherein the second layer includes a particulate acrylic polymer having a glass transition temperature of 20°° C. to 50° C. The separator for a secondary battery has good adhesion with the electrode and can solve the resistance problem in the presence of the inorganic particles.