Spirally-Wound Electrode Assembly Separator Adhesive Layer
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Solution Overview
Problem
The existing methods for forming a porous layer on separators for rechargeable lithium batteries using fluorine-based polymers result in separators with inadequate slip characteristics, leading to handling difficulties and potential distortion of spirally-wound electrode assemblies, which can compromise battery cycle-life.
Innovation Solution
A spirally-wound electrode assembly is designed with a separator featuring a porous film and an adhesive layer containing fluorine-based polymer particles and a binder, where the fluorine-based polymer particles are combined with a resin, such as acrylic resin, and the binder includes a polyolefin resin, with inorganic particles optionally added for improved porosity and thermal stability, to enhance the slip characteristics and prevent distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous layer is formed on the separator surface using fluorine-based polymer, then the battery cycle-life is improved, but the separator slip characteristics deteriorate and handling becomes difficult
Solution Approach 1:
The separator structure is segmented into two distinct layers: a base separator layer and a porous adhesive layer. This segmentation allows each layer to perform its specific function - the base separator provides structural support while the porous adhesive layer provides both the slip characteristics and adhesive properties needed for handling and battery performance
Solution Approach 2:
The separator uses a composite structure combining a base separator material with a porous adhesive layer containing fluorine-based polymer particles dispersed in an adhesive matrix. This composite material approach allows the separator to simultaneously achieve good slip characteristics from the base layer and enhanced adhesive properties from the porous layer, resolving the contradiction between handling ease and cycle-life
2Strength
If a porous layer is formed on the separator surface, then adhesive strength is improved, but slip characteristics deteriorate causing distortion of spirally-wound electrode assembly
Solution Approach 1:
The separator design applies local quality by creating a porous adhesive layer with specific properties (porosity, adhesive content) only on the surface where adhesion is needed, while maintaining the base separator's smooth surface for slip characteristics. This localized differentiation allows the separator to have different properties in different regions - adhesive where needed, slippery where needed
Solution Approach 2:
The composite structure of base separator plus porous adhesive layer allows simultaneous achievement of adhesive strength and slip characteristics. The base separator provides the smooth surface for slip while the porous adhesive layer provides localized adhesion, preventing distortion of the spirally-wound assembly
3Reliability
If fluorine-based polymer is used in the porous layer, then cycle-life is improved, but static electricity generation increases making handling difficult
Solution Approach 1:
The adhesive matrix acts as an intermediary between the fluorine-based polymer particles and the separator surface. It disperses the fluorine-based polymer particles uniformly and binds them to the separator, reducing static electricity generation while maintaining the cycle-life benefits of the fluorine-based polymer
Data Source
AI summary
A spirally-wound electrode assembly for a rechargeable lithium battery includes a positive electrode, a negative electrode and a separator between the positive electrode and the negative electrode, wherein the separator includes a porous film and an adhesive layer on at least one side of the porous film, and the adhesive layer includes a fluorine-based polymer-containing particulate and a binder. A rechargeable lithium battery includes the spirally-wound electrode assembly.