Aromatic Polyamide Battery Separator Coating for Thermal Shutdown Stability
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Solution Overview
Problem
Current lithium secondary battery separators, primarily made of polyolefin, fail to maintain shutdown effectiveness during localized internal short circuits due to melting at high temperatures, leading to potential fires or explosions, as they lack sufficient heat resistance and stability.
Innovation Solution
Aromatic polyamide composite separators are developed, incorporating glass fibers and aromatic polyamide with low thermal shrinkage and high heat resistance, coated onto fiberglass fabric, enhancing mechanical and thermal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyolefin separator is used, then shutdown effect is achieved at low temperature, but heat resistance is insufficient at high temperature
Solution Approach 1:
The patent uses a composite structure consisting of polyolefin microporous film and aromatic polyamide coating layer. The polyolefin base provides shutdown effect at low temperature, while the aromatic polyamide coating layer provides high-temperature heat resistance, combining the advantages of both materials to resolve the contradiction between shutdown effect and heat resistance.
Solution Approach 2:
The aromatic polyamide coating is applied locally on the surface of the polyolefin separator, creating different functional zones: the polyolefin substrate maintains shutdown effect, while the aromatic polyamide coating provides localized high-temperature resistance where it is most needed for preventing thermal runaway.
2Ease of manufacture
If polyolefin separator is used, then manufacturing simplicity is maintained, but thermal stability deteriorates at high temperature
Solution Approach 1:
The composite structure combines polyolefin's ease of manufacturing with aromatic polyamide's thermal stability. The polyolefin base can be produced using existing microporous film technology, while the aromatic polyamide coating adds thermal stability without requiring complete redesign of the manufacturing process.
Solution Approach 2:
The aromatic polyamide coating is applied in advance to the polyolefin separator surface, pre-establishing thermal protection before the separator encounters high-temperature conditions during battery operation, thus preventing thermal degradation before it occurs.
3Temperature
If aromatic polyamide coating is applied on polyolefin separator, then heat resistance is improved, but manufacturing complexity increases
Solution Approach 1:
The separator is divided into two functional segments: the polyolefin microporous film substrate and the aromatic polyamide coating layer. This segmentation allows each layer to be optimized independently and manufactured using relatively simple processes, reducing overall manufacturing complexity while maintaining high heat resistance.
Solution Approach 2:
The patent optimizes the coating thickness parameter of aromatic polyamide to balance heat resistance and manufacturing complexity. By controlling the coating thickness within a specific range, sufficient thermal protection is achieved without making the coating process overly complex or time-consuming.
4Device complexity
If separator structure is simplified, then manufacturing cost is reduced, but safety performance deteriorates at high temperature
Solution Approach 1:
The composite structure of polyolefin and aromatic polyamide provides enhanced safety performance through the synergistic effects of both materials. The polyolefin provides shutdown effect while the aromatic polyamide provides heat resistance, achieving high safety performance with a relatively simple two-layer composite structure that doesn't significantly increase manufacturing complexity.
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 aromatic polyamide composite separators exhibit improved thermal stability, reduced shrinkage, and increased safety by maintaining integrity at high temperatures, preventing large-area short circuits and enhancing the safety of lithium secondary batteries.
Implementation Method 1
Aromatic polyamide polymers (such as PPTA, PMIA, PBA, PSA) have a high heat-resistance performance with a glass transition temperature of above 300°C and thermal decomposition temperature up to 560°C
Implementation Method 2
thermal decomposition temperature up to 560°C
Data Source
Figure 1~2
AI summary
The invention relates to a composite separator containing an aromatic polyamide and a manufacturing method thereof, and a secondary battery. The composite separator containing an aromatic polyamide of the invention comprises a glass fiber and an aromatic polyamide. The composite separator has a thermal shrinkage percentage of less than 3% at 300°C. Also provided is a manufacturing method of a composite separator containing an aromatic polyamide. The composite separator of the invention exhibits excellent mechanical performance and heat resistance, and is especially applicable to secondary batteries.