Battery Separator Coating for Heat Resistance and Electrode Adherence
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving high energy density, cycle-life characteristics, and safety due to issues with electrode adherence and thermal contraction, particularly in down-sized batteries for applications like electric vehicles.
Innovation Solution
A separator for rechargeable lithium batteries is developed, comprising a porous substrate with a coating layer containing organic filler particles, fluorine organic binder particles, and (meth)acryl organic binder particles, where the average particle diameter of the organic filler particles is greater than or equal to that of the fluorine organic binder particles, and the coating layer is applied in a specific amount to enhance adherence and mechanical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the separator uses a conventional coating layer with inorganic filler particles, then heat resistance is improved, but electrode adherence deteriorates and internal resistance increases
Solution Approach 1:
The patent changes the fundamental parameter of filler particle material from inorganic to organic, and optimizes particle diameter parameters (organic filler ≥ fluorine binder) to simultaneously achieve heat resistance and electrode adherence. This parameter transformation resolves the contradiction by finding a new material state that satisfies both requirements.
Solution Approach 2:
The patent creates a composite coating layer combining organic filler particles, fluorine organic binder particles, and (meth)acryl organic binder particles. This composite structure integrates the heat resistance function of organic fillers with the adhesive properties of dual-binder systems, resolving the contradiction between thermal stability and electrode adherence.
2Strength
If the separator uses a thick coating layer to improve mechanical strength, then structural stability is improved, but porosity decreases and ion transport resistance increases
Solution Approach 1:
The patent employs a thin film coating layer (1-20 μm) that provides sufficient mechanical strength through optimized composition rather than thickness. The flexible organic binder system maintains film integrity while allowing high porosity (30-70%), resolving the contradiction between strength and porosity.
Solution Approach 2:
The patent designs the coating layer as a porous structure with controlled porosity (30-70%) through particle packing and binder selection. The porous architecture provides both mechanical integrity and ion transport pathways, simultaneously achieving strength and porosity requirements.
3Quantity of substance
If the separator uses organic filler particles with large particle diameter to maintain porosity, then ion transport is improved, but coating uniformity deteriorates
Solution Approach 1:
The patent applies local quality by using organic filler particles with specific diameter ranges (0.1-10 μm) that provide appropriate porosity in different regions of the coating. The particle size distribution creates localized pore structures that maintain both porosity and coating uniformity through controlled heterogeneity.
Solution Approach 2:
The patent optimizes the particle diameter parameter of organic fillers to a specific range (0.1-10 μm) that balances porosity maintenance with coating uniformity. This parameter optimization ensures particles are large enough to maintain pore structure but small enough to achieve uniform distribution and coating.
4Stability of the object's composition
If the separator uses conventional binder content to ensure coating adhesion, then coating integrity is improved, but moisture absorption increases and cycle life deteriorates
Solution Approach 1:
The patent extracts the harmful moisture-absorbing property from the binder system by selecting fluorine organic binders with low moisture affinity. This extraction of the detrimental characteristic maintains coating integrity while eliminating moisture absorption that would harm cycle life.
Solution Approach 2:
The patent creates a composite binder system combining fluorine organic binder particles and (meth)acryl organic binder particles in specific ratios. This composite binder provides both coating adhesion and low moisture absorption, simultaneously achieving coating integrity and cycle life requirements.
Data Source
AI summary
A separator for a rechargeable lithium battery and a rechargeable lithium battery including the separator, the separator including a porous substrate; and a coating layer on at least one surface of the porous substrate, wherein the coating layer includes organic filler particles, fluorine organic binder particles, and (meth)acryl organic binder particles, an average particle diameter of the organic filler particles is equal to or greater than an average particle diameter of the fluorine organic binder particles, and the fluorine organic binder particles are coated on the porous substrate as a part of the coating layer in an amount of less than about 0.1 g/m2 per surface.