Separator Adhesion Control via Peel Strength Ratio
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Solution Overview
Problem
Existing electrochemical devices, such as lithium secondary batteries, face safety issues due to heat shrinkage of polyolefin-based separators leading to short-circuits, and increased adhesive layer thickness degrades output characteristics and adhesion between electrodes and separators.
Innovation Solution
An electrode assembly with a porous polymer substrate, a porous coating layer containing inorganic particles and a binder polymer, and an adhesive layer, where the Peel Strength is higher than the Lami Strength, ensuring enhanced adhesion and scratch resistance while maintaining optimal ion conductivity and battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the loading amount of adhesive slurry is increased to increase the Lami Strength, then the adhesion between electrode and separator is improved, but the thickness of the adhesive layer is increased and the content of binder polymer is increased to cause pore blocking, thereby increasing separator resistance and degrading output characteristics
Solution Approach 1:
The patent changes the key parameter from Lami Strength to Peel Strength, and establishes a specific ratio relationship (Peel Strength/Lami Strength = 1.05 to 2.0) to optimize both adhesion and ion conductivity. This parameter transformation resolves the contradiction by finding a new control variable that correlates with both objectives.
Solution Approach 2:
The patent applies different functional requirements to different aspects of adhesion: Peel Strength controls the bonding between separator layers (affecting structural integrity and scratch resistance), while Lami Strength controls the bonding between separator and electrode. By differentiating these local adhesion qualities and their relative importance, the patent optimizes the adhesive composition without excessive thickness.
2Strength
If the thickness of the adhesive layer is increased to improve adhesion, then the Lami Strength is improved, but the pore blocking is increased and the ion conductivity is degraded
Solution Approach 1:
The patent transforms the control parameter from adhesive layer thickness to the Peel Strength/Lami Strength ratio, which indirectly controls thickness through composition optimization. This allows achieving sufficient adhesion with minimal thickness, preventing pore blocking while maintaining ion conductivity.
3Stability of the object's composition
If the Peel Strength is maintained at a predetermined level to prevent separation of inorganic particles, then the coating layer stability is improved, but the adhesion between electrode and separator is insufficient and the separator surface is scratched
Solution Approach 1:
The patent elevates Peel Strength from a baseline maintenance parameter to the primary control parameter, and establishes its quantitative relationship with Lami Strength through the ratio Peen Strength/Lami Strength = 1.05 to 2.0. This ensures both coating layer stability and sufficient electrode-separator adhesion are achieved simultaneously.
Solution Approach 2:
The patent proactively designs the adhesive composition to achieve the optimal Peel Strength/Lami Strength ratio before assembly, preventing both coating layer separation and insufficient adhesion issues. This preemptive parameter optimization avoids the need for excessive adhesive thickness that would cause pore blocking.
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 solution improves adhesion between the separator and electrode, increases scratch resistance, and maintains battery performance by controlling the ratio of Peel Strength to Lami Strength within a specific range, preventing pore blocking and degradation of ion conductivity.
Implementation Method 1
a porous coating layer formed on at least one surface of the porous polymer substrate and containing a plurality of inorganic particles and a binder polymer positioned on the whole or a part of the surface of the inorganic particles to connect the inorganic particles with each other and fix them
Implementation Method 2
an adhesive layer formed on at least one surface of the separator base, provided to face either of the electrodes and containing an adhesive resin
Data Source
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AI summary
Disclosed is an electrode assembly including two electrodes having polarities opposite to each other, and a separator interposed between the two electrodes, wherein the separator includes: a separator base which includes a porous polymer substrate having a plurality of pores, and a porous coating layer; and an adhesive layer formed on at least one surface of the separator base, provided to face either of the electrodes and containing an adhesive resin, and wherein the adhesion (Peel Strength) between the porous polymer substrate and the porous coating layer and the adhesion (Lami Strength) between the adhesive layer and the electrode satisfy Mathematical Formula 1. An electrochemical device including the electrode assembly is also disclosed. In the electrode assembly, the separator shows increased resistance against scratching and the adhesion between the separator and the electrode can be improved.