Coated Battery Separator Balancing Porosity and Thickness Stability
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Solution Overview
Problem
Existing separators for electrochemical devices face challenges in maintaining high porosity, which leads to decreased mechanical strength and increased thickness variation, affecting the performance and safety of the device.
Innovation Solution
A separator with a porous polymer substrate and a coating layer containing a polymer binder and inorganic particles is developed, with controlled porosity between 50% to 65%, thickness of 8 μm to 15 μm, and electrical resistance of 0.1 ohm to 0.6 ohm, to improve resistance and minimize thickness variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the porosity of the porous polymer substrate is increased to improve ion transport and reduce resistance, then the electrical resistance decreases, but the mechanical strength and thickness stability deteriorate
Solution Approach 1:
The patent employs a composite structure consisting of a porous polymer substrate combined with a coating layer containing inorganic particles (such as alumina, boehmite, or aluminum hydroxide) and polymer binder. This composite design allows the substrate to maintain high porosity (50-65%) for excellent ion transport and low electrical resistance, while the coating layer provides mechanical reinforcement to prevent thickness variation and improve overall structural strength. The synergistic combination resolves the contradiction between electrical performance and mechanical stability.
Solution Approach 2:
The patent utilizes a porous polymer substrate with controlled porosity in the range of 50-65%, which optimizes the balance between ion transport efficiency and mechanical integrity. The porous structure facilitates rapid lithium ion movement, reducing electrical resistance, while the specific porosity range is maintained through careful control of substrate fabrication parameters to ensure adequate mechanical strength without requiring excessive coating thickness.
2Reliability
If the porosity of the porous polymer substrate is increased to improve ion transport, then the electrical resistance decreases, but the thickness variation increases
Solution Approach 1:
The coating layer acts as a stabilizing shell over the porous substrate, compensating for thickness variations that would otherwise occur in high-porosity structures. The inorganic particles and binder in the coating layer create a more uniform external surface, reducing thickness variation while allowing the internal porous structure to maintain optimal porosity for low electrical resistance.
3Quantity of substance
If the thickness of the separator is reduced to improve energy density, then the energy density increases, but the mechanical strength and safety decrease
Solution Approach 1:
The composite structure with coating layer provides enhanced mechanical strength and thermal stability, enabling the use of thinner separator substrates without compromising safety. The coating layer acts as a protective barrier that maintains structural integrity even at reduced thickness, allowing optimization of energy density while preserving mechanical strength and safety characteristics.
Solution Approach 2:
The patent optimizes the thickness parameters of both the porous substrate and coating layer to achieve the desired balance. By controlling substrate thickness and coating thickness within specific ranges, the design achieves maximum energy density while maintaining adequate mechanical strength and safety performance through the synergistic effect of the composite structure.
Data Source
AI summary
A separator for an electrochemical device according to one embodiment of the present disclosure includes: a porous polymer substrate; and a coating layer provided on at least one surface of the porous polymer substrate, and including a polymer binder and inorganic particles, in which the porosity of the porous polymer substrate is about 50% to 65%.