Three-Layer Separator for Lithium Ion Battery Thermal Stability
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Solution Overview
Problem
Lithium ion batteries face challenges in achieving high thermal stability and safety performance, particularly in terms of heavy impact resistance, due to the requirement for higher rate performance which compromises their safety and thermal stability.
Innovation Solution
A three-layered porous substrate separator is developed, where the second porous substrate has a lower melting point than the first and third substrates, enhancing thermal stability by blocking lithium ion flow when heated, and the tensile strength in the machine direction exceeds that in the transverse direction for improved safety, with an optional porous layer for enhanced adhesion and mechanical support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the rate performance of lithium-ion batteries is increased to pursue high energy density, then the energy density is improved, but the thermal stability and safety performance (such as heavy impact resistance) deteriorate
Solution Approach 1:
The separator is divided into three distinct porous substrates with different melting points arranged in sequence. The first porous substrate (150-350°C), second porous substrate (110-150°C), and third porous substrate (150-350°C) work together to provide progressive thermal protection while maintaining ion conductivity for high rate performance
Solution Approach 2:
The separator uses a composite structure combining multiple porous substrates made from different materials (polyethylene, atactic polypropylene, isotactic polypropylene, polyvinylidene fluoride, polyethylene terephthalate, cellulose, polyimide, polyamide, spandex, and polyphthalamide) to achieve both high energy density and improved thermal stability
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 significantly improves thermal stability and safety performance by preventing electrode short-circuiting and enhancing impact resistance, as demonstrated by improved pass rates in thermal and impact tests.
Implementation Method 1
the second porous substrate comprises at least one of polyethylene and atactic polypropylene... the second porous substrate has a melting point of 110 °C to 150 °C
Data Source
Figure 1~4
AI summary
The present application provides a separator and a lithium ion battery, the separator comprises a first porous substrate, a second porous substrate and a third porous substrate, wherein the second porous substrate is arranged between the first porous substrate and the third porous substrate, and a tensile strength of the separator in a machine direction is greater than a tensile strength of the separator in a transverse direction. The use of the separator of the present application can improve the thermal stability and safety performance of the lithium ion battery.