Lithium Battery Separator Coating Balancing Shrinkage and Resistance
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving high energy density and capacity while maintaining stability and reducing heat shrinkage and membrane resistance.
Innovation Solution
A separator for lithium batteries comprising a porous substrate with a coating layer containing a (meth)acryl-based binder and a mixture of boehmite and barium titanate, optimized in weight ratio and particle size, to enhance thermal stability and ionic conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a separator is used in rechargeable lithium batteries, then thermal stability is improved, but membrane resistance increases
Solution Approach 1:
The patent applies composite materials by combining boehmite and barium titanate in a specific weight ratio (20:80 to 80:20) within the coating layer. This composite filler system provides both thermal stability through boehmite's high heat resistance and low membrane resistance through barium titanate's ionic conductivity, resolving the contradiction between thermal stability and membrane resistance.
Solution Approach 2:
The patent utilizes parameter changes by optimizing the particle size of boehmite and barium titanate (D50: 100-500 nm) and their weight ratio (20:80 to 80:20). These parameter optimizations enable the coating layer to achieve both low dry shrinkage rate (improved thermal stability) and low membrane resistance, simultaneously addressing both requirements.
2Stability of the object's composition
If the separator undergoes heat treatment to reduce shrinkage, then thermal stability is improved, but membrane resistance increases
Solution Approach 1:
The patent employs composite materials (boehmite + barium titanate) in the coating layer that inherently provide both dimensional stability (low dry shrinkage) and ionic conductivity (low membrane resistance). This composite approach eliminates the need for aggressive heat treatment while achieving both goals simultaneously.
Solution Approach 2:
The coating layer acts as an intermediary between the porous substrate and the electrolyte, providing a controlled interface that reduces dry shrinkage without creating resistance barriers. The specific composite filler system mediates between thermal stability requirements and ionic conductivity requirements.
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 achieves low dry shrinkage rates and reduced membrane resistance, improving the battery's thermal stability and ionic conductivity, thereby enhancing its performance and lifespan.
Implementation Method 1
The separator may have a low membrane resistance and a high heat resistance, resulting in low heat shrinkage
Implementation Method 2
The separator having a low membrane resistance
Data Source
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AI summary
Examples of the present disclosure include a separator for a rechargeable lithium battery, and a rechargeable lithium battery including the separator. The separator for a rechargeable lithium battery includes a porous substrate and a coating layer on at least one surface of the porous substrate. The coating layer includes a binder and a filler. The binder includes a (meth)acryl-based binder including a sulfonate group-containing structural unit. The filler includes a mixture of boehmite and barium titanate in a weight ratio in a range of 20:80 to 80:20 with respect to 100 parts by weight of the mixture of boehmite and barium titanate.