Composite Lithium-Cell Separator for Heat Stability and Ion Flow
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Solution Overview
Problem
Lithium batteries face safety concerns due to heat generation, electrolyte flammability, and the need for efficient heat management, requiring a separator that is heat-resistant, mechanically stable, and prevents short circuits while maintaining power output and dimensional integrity.
Innovation Solution
A composite separator comprising a non-woven polyester support, a porous layer of polyvinylidene fluoride (PVDF) or its derivatives, and a layer of UV-curing or thermal-curing polymers such as polydimethylsiloxane (PDMS) or epoxy, which provides heat resistance, dimensional stability, and adjustable gas permeation rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separator is designed to be heat-resistant and mechanically stable, then safety and structural integrity are improved, but gas permeation rate may decrease and power output may be reduced
Solution Approach 1:
The patent employs a composite separator structure consisting of a non-woven polyester support layer combined with a PVDF porous coating layer. This composite material approach allows the separator to simultaneously achieve high heat resistance (maintaining structural integrity at elevated temperatures) and adequate gas permeation rates (maintaining power output). The polyester support provides mechanical strength and thermal stability, while the PVDF porous layer ensures ion transport efficiency.
2Reliability
If the separator coating weight is increased to improve heat resistance and mechanical properties, then safety is improved, but gas permeation rate decreases and power output is reduced
Solution Approach 1:
The patent optimizes the coating weight parameter of the PVDF porous layer to a specific range (35.6-89 g/m2) to achieve the best balance between heat resistance and gas permeation. By precisely controlling this parameter, the separator attains sufficient mechanical strength and thermal stability while maintaining adequate ion transport capability to support high power output.
Solution Approach 2:
The patent applies a porous PVDF coating layer specifically on the polyester support where it is most needed for heat resistance, rather than using a uniformly thick separator throughout. This localized application of functional material ensures that heat-resistant properties are enhanced at the critical separation interface while minimizing the impact on overall gas permeation and power output.
3Ease of manufacture
If the separator uses a single material to simplify structure, then manufacturing is easier, but it cannot simultaneously achieve heat resistance, mechanical stability, and high gas permeation rate
Solution Approach 1:
The patent uses a two-layer composite structure with non-woven polyester support and PVDF porous coating. This composite approach enables the separator to simultaneously achieve heat resistance from the polyester, mechanical stability from both layers, and high gas permeation rate from the porous PVDF structure, which would be difficult to accomplish with a single material.
4Productivity
If the separator is made thinner to improve ion transport, then gas permeation rate is improved, but mechanical strength and heat resistance decrease
Solution Approach 1:
The patent employs a composite structure where a thin PVDF porous coating layer (providing high gas permeation) is supported by a stronger non-woven polyester substrate (providing mechanical strength). This allows the separator to achieve high ion transport efficiency while maintaining sufficient mechanical integrity and heat resistance through the supporting polyester layer.
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 composite separator effectively enhances the safety and performance of lithium batteries by maintaining structural integrity and gas permeation rates even at high temperatures, preventing overheating and short circuits, thus ensuring reliable operation.
Implementation Method 1
The porous layer of polyvinylidene fluoride (PVDF) or its derivatives has a melting point of 160-175° C.
Implementation Method 2
a layer of UV-curing or thermal-curing polymers formed on top of the porous layer of polyvinylidene fluoride (PVDF) or its derivatives
Implementation Method 3
a layer of UV-curing or thermal-curing polymers formed on top of the porous layer of polyvinylidene fluoride (PVDF) or its derivatives
Data Source
AI summary
In an embodiment of the disclosure, a separator utilized in a lithium battery is provided. The separator includes a non-woven polyester support, a porous layer of polyvinylidene fluoride (PVDF) or its derivatives formed on the non-woven polyester support, a layer of UV-curing or thermal-curing polymers formed on top of the porous layer of polyvinylidene fluoride (PVDF) or its derivatives.