Battery Separator Composition for Rapid Thermal Shutdown
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Solution Overview
Problem
Lithium-ion batteries face challenges in high-temperature safety performance due to the poor stability and heat resistance of high-voltage positive electrodes and fast-charging graphite, leading to uncontrolled reactions and heat generation, which can cause safety issues.
Innovation Solution
The use of a separator with a porous substrate composed of specific polyethylene resin materials with controlled melting enthalpy and mass percentages, along with additional high-temperature resistant resins, to achieve rapid shutdown and maintain strength, thereby enhancing safety and electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-voltage positive electrodes and fast-charging graphite are used to improve energy density and fast-charging performance, then energy density and fast-charging performance are improved, but heat resistance and stability deteriorate, leading to intensified reactions with electrolyte and increased heat generation
Solution Approach 1:
The patent introduces a specially designed separator as an intermediary component between the positive and negative electrodes. This separator includes a porous substrate with specific polyethylene resin materials (first and second resins with different melting enthalpies) that acts as a mediator to prevent direct contact and harmful reactions between electrodes at high temperatures, while still allowing ion transport during normal operation. The separator melts and closes pores at controlled temperatures to stop heat and substance diffusion.
Solution Approach 2:
The separator is constructed as a composite material system combining a porous substrate with multiple polyethylene resin materials having different melting enthalpies (first resin: 110-160 J/g, second resin: 170-205 J/g). This composite structure enables multi-stage thermal response, where the first resin provides initial shutdown protection at lower temperatures and the second resin provides additional protection at higher temperatures, solving the contradiction between fast charging and heat resistance.
2Ease of manufacture
If the separator uses conventional single-material structure, then manufacturing is simple, but shutdown response is slow and cannot effectively prevent heat and substance diffusion at high temperatures
Solution Approach 1:
The separator's porous substrate is segmented into multiple functional resin components with distinct melting enthalpy values. The first polyethylene resin material (110-160 J/g) and second polyethylene resin material (170-205 J/g) are distributed within the substrate to create distinct thermal response zones. This segmentation enables the separator to respond at multiple temperature stages, significantly improving shutdown response speed and effectiveness while maintaining manufacturing feasibility through established composite material processing techniques.
3Reliability
If the separator achieves rapid shutdown at low temperature, then high-temperature safety performance is improved, but separator strength may be compromised
Solution Approach 1:
The patent carefully controls the melting enthalpy parameters of the polyethylene resin materials within specific ranges (first resin: 110-160 J/g, second resin: 170-205 J/g) and their mass percentages (first resin: 10-40%, second resin: 45-88%). By optimizing these parameters, the separator achieves rapid shutdown at appropriate temperatures while maintaining sufficient mechanical strength for normal battery operation. The controlled parameter ranges ensure that the separator melts at the right temperature to stop ion transport but remains strong enough to prevent electrode short circuits during assembly and operation.
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 separator effectively shuts down at lower temperatures, preventing heat and substance diffusion, improving high-temperature safety and electrochemical performance by balancing shutdown rate and strength, thus enhancing battery safety.
Implementation Method 1
A melting enthalpy of the first polyethylene resin material is 110 J/g to 160 J/g... A melting enthalpy of the second polyethylene resin material is 170 J/g to 205 J/g... the separator can achieve rapid shutdown at a relatively low temperature as the electrochemical apparatus heats up
Data Source
AI summary
An electrochemical apparatus includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. The separator is disposed between the positive electrode plate and the negative electrode plate, the separator includes a porous substrate, and the porous substrate includes a first polyethylene resin material and a second polyethylene resin material; where a melting enthalpy of the first polyethylene resin material is 110 J/g to 160 J/g, a melting enthalpy of the second polyethylene resin material is 170 J/g to 205 J/g, and a shutdown rate of the separator is 10 kΩ/min to 80 kΩ/min; based on the mass of the porous substrate, a mass percentage of the first polyethylene resin material is 10% to 40%, and a mass percentage of the second polyethylene resin material is 45% to 88%.