Porous Separator Adhesive Layer for Low-Shrinkage Li-Ion Batteries
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium secondary batteries face issues with shape stability and air permeability due to thermal shrinkage and inadequate adherence of separators, particularly when using polyvinyl alcohol as an adhesive, which affects charge and discharge characteristics.
Innovation Solution
A separator with a porous adhesive layer formed on a porous substrate, using polyvinylidene fluoride-based polymer microparticles and a nitrogen-containing binder, applied as a thin film to ensure excellent adherence and maintain shape stability, with a thickness of 1 μm or less, improving air permeability and thermal shrinkage resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyvinyl alcohol is used as an adhesive to adhere the electrode to the separator, then adherence is improved, but thermal shrinkage rate increases and air permeability deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive layer by using polyvinylidene fluoride-based polymer microparticles instead of polyvinyl alcohol, and controls the thickness parameter at 1 μm or less. This parameter change resolves the contradiction by achieving both good adherence and reduced thermal shrinkage rate, while maintaining air permeability characteristics.
Solution Approach 2:
The patent creates a composite adhesive layer combining polyvinylidene fluoride-based polymer microparticles with a nitrogen-containing binder. This composite material approach allows the adhesive layer to simultaneously provide strong adherence, thermal stability, and maintained air permeability, resolving the contradictions between these properties.
2Strength
If polyvinyl alcohol is used as an adhesive, then adherence is improved, but air permeability increases
Solution Approach 1:
The patent changes the material composition parameter by replacing polyvinyl alcohol with polyvinylidene fluoride-based polymer microparticles and controls the thickness parameter at 1 μm or less. This resolves the contradiction by achieving good adherence while preventing excessive air permeability, maintaining the porous substrate characteristics.
Solution Approach 2:
The patent uses a porous adhesive layer with controlled porosity to maintain air permeability while providing adherence. The porous structure allows gas transport through the separator without compromising the bonding strength between electrode and separator.
3Strength
If adhesive layer thickness is increased to improve adherence, then adherence is improved, but shape stability deteriorates
Solution Approach 1:
The patent optimizes the thickness parameter of the adhesive layer to 1 μm or less, which is a critical parameter change. This thin film configuration provides sufficient adherence while preventing thermal shrinkage and maintaining the shape stability of the battery after charge and discharge cycles.
Data Source
AI summary
The present invention relates to a separator, a manufacturing method therefor, and a lithium secondary battery comprising the same, the separator comprising: a porous substrate; and a porous adhesive layer formed on one surface or both surfaces of the porous substrate, wherein the porous adhesive layer comprises a nitrogen-containing binder and polyvinylidene fluoride-based polymer microparticles having an average diameter of 200 nm to 700 nm, and the total thickness of the porous adhesive layer is 1 μm or less.