Free-Standing Battery Separator With Crystalline Binder Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing porous polymer films used as separators in lithium secondary batteries suffer from low heat resistance, dimensional changes, increased interfacial resistance, and lithium deposition due to swelling, leading to safety issues and processability challenges.
Innovation Solution
A free-standing separator composed of inorganic particles and a binder resin with improved crystallinity, featuring a porous structure and controlled porosity, is developed to enhance tensile strength and minimize dimensional changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a free standing type separator merely including an inorganic material and a binder resin is applied, then heat shrinking properties and safety are improved, but the separator undergoes an increase in thickness and dimensional change due to volumetric swelling
Solution Approach 1:
The patent applies parameter changes by controlling the crystallinity of the binder resin to be 30% or more and using specific inorganic particles with controlled size distribution (0.1-10 μm). These parameter optimizations reduce volumetric swelling to 5% or less, thereby minimizing dimensional changes while preserving the heat resistance and safety benefits of the inorganic-based free standing separator structure.
2Reliability
If a free standing type separator merely including an inorganic material and a binder resin is applied, then heat shrinking properties and safety are improved, but the separator is spaced apart from an electrode to generate air bubbles, increasing interfacial resistance
Solution Approach 1:
The patent applies local quality by creating a porous structure with controlled pore size (0.01-1 μm) and porosity (30-70%) in specific regions of the separator. This localized pore structure allows electrolyte penetration and improves contact with electrodes, reducing interfacial resistance and lithium deposition while maintaining the overall free standing inorganic structure for heat resistance.
3Ease of manufacture
If the tensile strength of a separator is increased to ensure processability, then ease of manufacture is improved, but the separator may undergo dimensional change due to swelling
Solution Approach 1:
The patent applies composite materials by combining inorganic particles (70-95 wt%) with a binder resin (5-30 wt%) where the binder resin has controlled crystallinity (30% or more). This composite structure provides both the tensile strength needed for processability and the dimensional stability required, as the crystalline binder resin reduces swelling while the inorganic particles provide structural integrity.
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 maintains structural integrity, reduces resistance, and ensures stable performance by minimizing swelling and maintaining porosity, thereby enhancing safety and processability in battery assembly.
Implementation Method 1
the binder resin has a crystallinity of 30% or more
Implementation Method 2
an insulating porous layer including inorganic particles and a binder resin
Data Source
AI summary
Disclosed is a separator which essentially includes inorganic particles and a binder resin, can be used as a free standing type separator including no separator substrate, such as a polymer resin film, and causes no problem of heat shrinking. In addition, the separator has increased tensile strength by virtue of the improvement of the crystallinity of the binder resin through elongation, and shows a small dimensional change after being impregnated with an electrolyte.