Battery Separator Coating With Core-Shell Polyimide for Wet Heat Stability
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Solution Overview
Problem
Conventional methods for enhancing the thermal resistance of separators in lithium batteries fail to adequately address wet thermal shrinkage, which can lead to mechanical damage and potential battery explosions due to high temperatures.
Innovation Solution
A coating layer composition for lithium battery separators is developed, comprising a heat-resistant binder, hydroxy group-containing polyimide particles, and a functional group-containing silane cross-linking agent, forming a core-shell structured organic particle that improves adhesion and heat resistance without using inorganic particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional methods are used to enhance thermal resistance of separators, then heat resistance is improved, but wet thermal shrinkage resistance is insufficient leading to mechanical damage
Solution Approach 1:
The patent uses a composite coating layer comprising polyimide particles (providing heat resistance), silane crosslinking agent (forming three-dimensional network for shrinkage resistance), and binder (ensuring adhesion). This composite structure simultaneously achieves both heat resistance and wet thermal shrinkage resistance by combining materials with complementary properties.
Solution Approach 2:
The patent optimizes the molecular weight of polyimide (10,000-1,000,000), the ratio of crosslinking agent to polyimide (0.1-10:1), and the coating thickness (1-10 μm) to achieve the desired balance between heat resistance and shrinkage resistance. These parameter adjustments allow the coating to maintain structural integrity at high temperatures while resisting thermal shrinkage in wet environments.
2Temperature
If inorganic particles are used to improve heat resistance, then thermal stability is enhanced, but adhesive characteristics deteriorate
Solution Approach 1:
The patent replaces expensive inorganic particles with organic polyimide particles that provide comparable heat resistance. The polyimide particles form a coating that inherently bonds well with the separator substrate, eliminating the adhesion problems associated with inorganic particle coatings while maintaining thermal stability.
Solution Approach 2:
The patent uses polyimide with controlled molecular weight (10,000-1,000,000) and specific functional groups that enhance both thermal stability and adhesion to the separator. The molecular weight and chemical structure are optimized to ensure the coating maintains strong adhesive characteristics while providing the required thermal resistance.
3Temperature
If separator coating is applied to improve heat resistance, then thermal performance is enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent applies the coating formulation directly to the separator surface in a single step, where the silane crosslinking agent and polyimide particles self-assemble and crosslink upon contact with moisture or heat. This preliminary action approach eliminates the need for complex multi-step manufacturing processes, specialized equipment, or precise control conditions, thereby reducing manufacturing complexity while achieving the desired heat resistance.
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 effectively enhances the heat resistance and adhesive properties of the separator, preventing rapid contraction and deformation at elevated temperatures, thereby improving the safety and performance of lithium batteries.
Implementation Method 1
a functional group-containing silane cross-linking agent... the shell portion is on the surface of the core portion
Implementation Method 2
enhances the heat resistance... preventing rapid contraction and deformation at elevated temperatures
Data Source
AI summary
This application relates to a coating layer composition and a coating layer formed using the coating layer composition. The coating layer composition includes a heat-resistant binder, a hydroxy group-containing polyimide particle, a silane cross-linking agent, and a solvent. The hydroxy group-containing polyimide particle and the functional group-containing silane cross-linking agent form a core-shell structured organic particle in which a core portion is derived from the hydroxy group-containing polyimide particles and a shell portion that is derived from the functional group-containing silane cross-linking agent. The shell portion is on the surface of the core portion in the core-shell structured organic particle. The application also relates to a separator for a rechargeable lithium battery and a rechargeable lithium battery including the separator having a coating layer formed using the coating layer composition.