Electrode Assembly Insulating Coating for Wet Separator Adhesion
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Solution Overview
Problem
Existing electrode assemblies in secondary batteries, particularly those used in electric vehicles, face issues with short circuits due to poor adhesion of insulating materials, leading to potential fires and explosions, as PVDF-based insulating materials separate or dissolve in electrolyte solutions, reducing adhesion strength between electrodes and separators.
Innovation Solution
An electrode assembly with an insulating coating portion on the outer periphery of the active material layer, using a binder with two types of adhesive binders having different glass transition temperatures, and inorganic particles to enhance adhesion strength between electrodes and separators, ensuring wet adhesion strength between 1 gf/20 mm to 20 gf/20 mm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PVDF-based insulating material is used to prevent short circuits, then insulating performance is improved, but adhesion strength deteriorates due to separation and dissolution in electrolyte solution
Solution Approach 1:
The patent uses a composite binder system comprising both PVDF-based resin and polyacrylonitrile-based resin in specific weight ratios (PVDF: 10-70 wt%, PAN: 30-90 wt%). This composite approach combines the insulating properties of PVDF with the excellent adhesion and electrolyte resistance of PAN, resolving the contradiction between insulating performance and adhesion strength. The synergistic effect of the two polymers prevents both short circuits and binder separation/dissolution issues.
2Reliability
If insulating layer is inserted to prevent short circuits, then safety is improved, but adhesion between electrode and separator deteriorates causing folding and contact
Solution Approach 1:
The patent modifies the binder composition parameters by incorporating polyacrylonitrile-based resin which exhibits superior adhesion to separator and resistance to electrolyte-induced dissolution. The specific compositional parameters (weight ratios of PVDF to PAN, molecular weight ranges) are optimized to ensure both insulating function and strong adhesion, preventing the folding and contact problems that arise from poor adhesion.
3Strength
If adhesion strength is increased to prevent separator folding, then structural stability is improved, but insulating performance may deteriorate
Solution Approach 1:
The composite binder system maintains the insulating performance by retaining PVDF-based resin (10-70 wt%) which provides the necessary insulation properties, while simultaneously incorporating polyacrylonitrile-based resin (30-90 wt%) that enhances adhesion strength. This balanced composite formulation ensures both structural stability and insulating performance without compromising either function.
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 insulating coating portion improves adhesion strength, preventing short circuits and reducing the risk of explosions and fires by maintaining separator adhesion even in the presence of electrolyte solutions, thereby enhancing safety.
Implementation Method 1
a binder with two types of adhesive binders having different glass transition temperatures
Data Source
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AI summary
The present disclosure relates to an electrode assembly with improved adhesion strength between a positive electrode and a separator by giving an adhesive property to an insulating coating portion and an insulating coating composition therefor. The electrode assembly according to an aspect of the present disclosure has high wet adhesion strength between the electrode and the separator and prevents folding of the separator, thereby improving safety of an electrochemical device.F