Cross-Linked Lithium Battery Separator Coating for Low Shrinkage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Rechargeable lithium batteries face challenges in maintaining stability and high-temperature lifetime characteristics due to high shrinkage rates in the electrolyte and dry conditions, which can weaken mechanical properties.
Innovation Solution
A separator for rechargeable lithium batteries is developed with a coating layer comprising a cross-linked product of a (meth)acryl-based binder, aziridine-based cross-linking agent, and surface-modified filler with a particle diameter of 1.5 μm or less, enhancing bonding strength and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a conventional separator is used, then the battery can operate, but the separator exhibits high shrinkage rates in electrolyte and dry conditions, leading to reduced mechanical integrity and stability
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition and physical properties of the coating layer. Specifically, it uses a (meth)acryl-based binder with controlled molecular weight and functional groups, combines it with specific fillers (alumina, silica, boehmite) in optimized ratios, and applies controlled cross-linking to achieve a coating layer that maintains dimensional stability while providing necessary mechanical properties. This resolves the contradiction by changing the material parameters to simultaneously reduce shrinkage rate and maintain stability.
Solution Approach 2:
The patent employs composite materials by creating a multi-component coating layer system. The coating layer comprises a (meth)acryl-based binder combined with inorganic fillers (alumina, silica, boehmite), cross-linking agents, and optional additives. This composite structure leverages the complementary properties of each component: the binder provides adhesion and flexibility, the fillers provide thermal stability and structural support, and the cross-linking agents enhance mechanical strength. This composite approach resolves the contradiction between reducing shrinkage and maintaining overall separator stability.
2Reliability
If the separator coating layer is enhanced for heat resistance, then high-temperature lifetime characteristics improve, but the complexity of the coating composition increases
Solution Approach 1:
The patent manages complexity by carefully controlling and specifying key parameters of the coating components. It defines the (meth)acryl-based binder with specific functional groups and molecular weight ranges, selects from a limited set of inorganic fillers with specified particle size distributions, and uses controlled cross-linking degrees. These parameter specifications ensure consistent high-temperature performance while avoiding unnecessary complexity by focusing on critical parameters rather than excessive component variety.
Solution Approach 2:
The patent applies local quality by optimizing the coating layer composition specifically for the regions and functions where it is most needed. The coating layer is designed with enhanced thermal stability and mechanical strength at the separator surface where it contacts electrodes and experiences highest stress during operation. The composition is tailored to provide heat resistance where temperature effects are most critical, while maintaining overall coating integrity. This targeted approach improves high-temperature lifetime characteristics without uniformly increasing complexity throughout the entire separator structure.
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 exhibits significantly low shrinkage rates in both dry conditions and when saturated with electrolyte, maintaining mechanical integrity and heat resistance, thereby improving battery stability and longevity.
Implementation Method 1
The coating layer includes a cross-linked product of a binder and a cross-linking agent
Implementation Method 2
a porous substrate
Data Source
AI summary
Examples of the present disclosure relates to a separator for a rechargeable lithium battery, and a rechargeable lithium battery including the separator. A separator for a rechargeable lithium battery includes a porous substrate and a coating layer located on at least one surface of the porous substrate. The coating layer includes a cross-linked product of a binder and a cross-linking agent, a filler, and an adhesive binder. The binder includes a (meth)acryl-based binder including a structural unit derived from (meth)acrylate or (meth)acrylic acid, a cyano group-containing structural unit, and a sulfonate group-containing structural unit. The cross-linking agent includes an aziridine-based cross-linking agent. The filler is surface-modified and has a particle diameter D100 of about 1.5 μm or less, and the adhesive binder includes a cross-linked aziridine-based adhesive binder.