Lithium Battery Separator Coating for Thermal Stability
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving high energy density and thermal stability due to limitations in separator materials that can prevent short-circuits while maintaining low internal resistance and cycle-life performance.
Innovation Solution
A separator for rechargeable lithium batteries is developed, comprising a porous substrate with a coating layer containing a binder resin with specific polymer structures and inorganic particles, which enhances heat resistance, mechanical strength, and adherence to the substrate, preventing short-circuits and maintaining low internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separator with high thermal stability is used, then safety and heat resistance are improved, but internal resistance increases and energy density decreases
Solution Approach 1:
The separator employs a composite structure consisting of a polyolefin base layer combined with a coating layer containing inorganic particles (such as alumina, silica, or boehmite) dispersed in a binder resin. This composite design provides high thermal stability through the inorganic coating while maintaining low internal resistance by optimizing the binder resin composition and coating thickness, thereby resolving the contradiction between thermal stability and energy density
Solution Approach 2:
The invention optimizes specific parameters including the weight ratio of binder resin to inorganic particles (typically 5-20 wt% binder resin), coating layer thickness (1-10 μm), and the molecular weight and functional groups of the binder resin. These parameter adjustments allow the separator to achieve both high thermal stability (preventing short circuits at elevated temperatures) and low internal resistance (maintaining high energy density)
2Temperature
If a coating layer with high inorganic particle content is applied, then heat resistance is improved, but mechanical strength and adherence may deteriorate
Solution Approach 1:
The coating layer is designed as a composite material where inorganic particles provide heat resistance while the binder resin matrix maintains mechanical integrity. The binder resin contains functional groups that adhere to both the inorganic particles and the polyolefin substrate, creating a cohesive composite structure that simultaneously achieves high heat resistance and adequate mechanical strength
Solution Approach 2:
The invention carefully controls the binder resin content in the coating layer at 5-20 wt% of the total coating layer weight. This optimized parameter ensures sufficient inorganic particle content for heat resistance (80-95 wt% inorganic particles) while maintaining enough binder resin to provide mechanical strength and adherence. The molecular weight of the binder resin is also controlled (10,000-100,000 g/mol) to balance mechanical properties and thermal stability
3Reliability
If the coating layer thickness is increased, then thermal stability is improved, but internal resistance increases
Solution Approach 1:
The invention optimizes the coating layer thickness within a specific range of 1-10 μm. This controlled thickness parameter provides sufficient thermal stability to prevent membrane rupture at elevated temperatures while minimizing the additional resistance introduced by the coating layer. Thinner coatings (1-5 μm) are used when high energy density is prioritized, while thicker coatings (5-10 μm) are used when maximum thermal stability is required
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 provides a rechargeable lithium battery with improved thermal stability, cycle-life characteristics, and safety by ensuring excellent heat resistance and mechanical strength, while preventing short-circuits and maintaining low internal resistance.
Implementation Method 1
a coating layer on at least one surface of the porous substrate, wherein the coating layer includes a binder resin and inorganic particles
Implementation Method 2
The separator may electrically insulate the positive and negative electrodes, and may include micropores through which lithium ions move
Data Source
AI summary
A separator for a rechargeable lithium battery and a rechargeable lithium battery, the separator including a porous substrate; and a coating layer on at least one surface of the porous substrate coating layer on at least one surface of the porous substrate, wherein the coating layer includes a binder resin and inorganic particles, the binder resin includes a first polymer including a structural unit represented by Chemical Formula 1 and a second polymer including a structural unit represented by Chemical Formula 2, and a weight ratio of the first polymer and the second polymer in the binder resin is about 35:65 to about 75:25,