Separator Adhesive Layer Particle Sizing for Battery Resistance
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Solution Overview
Problem
Conventional separators for electrochemical devices, particularly lithium secondary batteries, face challenges with adhesion between the separator and electrodes when using aqueous slurry, leading to increased battery resistance and poor output characteristics due to heat shrinkage and phase separation issues.
Innovation Solution
A separator design featuring a porous polymer substrate with a porous coating layer containing inorganic particles and a binder polymer, combined with an adhesive layer comprising second inorganic particles and adhesive resin particles, where the weight ratio and size of these particles are optimized to maintain pore structure and reduce resistance during lamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous coating layer is formed by applying aqueous slurry containing inorganic particles and binder polymer, then the separator has significantly low resistance, but the adhesion between electrode and separator is weak
Solution Approach 1:
The invention uses a composite coating layer combining inorganic particles (such as alumina, silica, or boehmite) with binder polymer in a specific weight ratio range (inorganic particles: binder polymer = 90:10 to 99:1). This composite structure maintains the low resistance characteristic of aqueous slurry while the optimized composition provides sufficient adhesion strength to prevent electrode detachment during battery operation.
Solution Approach 2:
The invention optimizes the weight ratio of inorganic particles to binder polymer within a specific range (90:10 to 99:1) and controls the coating layer thickness (1-10 μm) to achieve the desired balance between low resistance and adequate adhesion. By adjusting these parameters, the separator maintains excellent electrical conductivity while providing sufficient mechanical bonding strength.
2Strength
If a porous coating layer is formed by applying organic slurry containing inorganic particles and binder polymer, then the adhesion between electrode and separator is improved, but the separator has significantly high resistance
Solution Approach 1:
The invention switches from organic slurry to aqueous slurry as the solvent system, which fundamentally changes the electrical resistance characteristics. The aqueous-based coating layer achieves significantly lower resistance while the optimized inorganic particle to binder polymer ratio (90:10 to 99:1) ensures adequate adhesion strength.
3Strength
If an adhesive layer is introduced onto the porous coating layer formed by aqueous slurry to increase adhesion, then the adhesion between separator and electrode is improved, but the battery shows significantly higher resistance after lamination
Solution Approach 1:
The invention removes the separate adhesive layer that was previously introduced on top of the porous coating layer. Instead, the adhesion function is integrated into the porous coating layer itself by optimizing its composition (inorganic particles to binder polymer ratio of 90:10 to 99:1). This eliminates the additional resistance layer while maintaining sufficient adhesion strength.
Solution Approach 2:
The invention combines the adhesion function and the low-resistance coating function into a single integrated porous coating layer. The optimized composition of inorganic particles and binder polymer in aqueous slurry provides both adequate adhesion strength and low electrical resistance, eliminating the need for a separate adhesive layer that would increase resistance.
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 enhances adhesion between the separator and electrodes while minimizing resistance increments, maintaining pore structure and ensuring stable battery performance under high temperature/high pressure conditions.
Implementation Method 1
a porous coating layer containing a plurality of first inorganic particles and a binder polymer positioned on the whole or a part of the surface of the first inorganic particles to connect and fix the first inorganic particles with each other
Implementation Method 2
the diameter of the adhesive resin particles is 1.1-3.5 times a diameter of the second inorganic particles... maintaining the pores of the adhesive layer after the lamination of an electrode
Data Source
AI summary
A separator which includes: a porous polymer substrate having a plurality of pores; a separator base including a porous coating layer formed on at least one surface of the porous polymer substrate; and an adhesive layer formed on at least one surface of the separator base, said adhesive layer comprising a plurality of second inorganic particles and adhesive resin particles, wherein the weight ratio of the second inorganic particles to the adhesive resin particles is 5:95-60:40, and the diameter of the adhesive resin particles is 1.1-3.5 times the diameter of the second inorganic particles. An electrochemical device including the separator is also disclosed. The separator shows improved adhesion between an electrode and the separator, maintains the pores of the adhesive layer even after a process of electrode lamination, and improves the resistance of an electrochemical device.