Composite Separator Press-Fit for Wrinkle-Resistant Lithium Cells
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing polyethylene (PE) or polypropylene (PP) separators in lithium-ion batteries do not fit tightly to the electrode sheets, leading to wrinkling and increased internal resistance, which affects electrical and safety performance.
Innovation Solution
A composite separator with porous substrate layers and non-adhesive polymers C1 and C2 is used, where the polymers form protruding structures to tightly fit with the electrode sheets through controlled press-fit processing, ensuring stable bonding and structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a PE or PP separator is used, then the separator can provide a microporous structure for lithium ion movement, but it does not fit tightly to the electrode sheets causing wrinkling and increased internal resistance
Solution Approach 1:
The invention uses a porous substrate layer as the base structure of the composite separator, which provides the necessary microporous structure for lithium ion movement. The porosity is maintained while adding functional layers that enable tight fitting to electrode sheets, resolving the contradiction between ion transport capability and bonding stability.
Solution Approach 2:
The invention creates a composite separator by combining a porous substrate layer with functional active layers containing non-adhesive polymers. This composite structure integrates the ion-conducting properties of porous materials with the bonding capabilities of the active layers, eliminating wrinkling and reducing internal resistance while maintaining reliable lithium ion transport.
2Reliability
If the separator surface is made smooth for tight fitting, then bonding is improved, but lithium ion transport channels may be reduced
Solution Approach 1:
The invention applies different properties to different parts of the separator structure. The functional active layers provide local bonding capability at the interface with electrode sheets, while the bulk porous substrate layer maintains the microporous structure for lithium ion transport. This local differentiation resolves the contradiction between bonding strength and ion transport channel preservation.
Solution Approach 2:
The separator is segmented into distinct functional layers: a porous substrate layer for ion transport and functional active layers for bonding. This segmentation allows each layer to optimize its specific function without compromising the other, ensuring both tight fitting and adequate lithium ion transport channels.
3Reliability
If non-adhesive polymers with large particle size are used, then protruding structures form for better fitting, but the coating thickness must be increased
Solution Approach 1:
The invention optimizes the particle size parameter of non-adhesive polymers within a specific range (D50: 2-10 μm) to form effective protruding structures for tight fitting. By carefully controlling this parameter, the patent achieves good bonding without requiring excessive coating thickness, resolving the contradiction between fitting tightness and coating thickness.
Data Source
AI summary
Provided in the present disclosure is a cell, including a positive electrode sheet, a composite separator and a negative electrode sheet provided in sequence. The positive electrode sheet includes a first positive electrode active coating. The negative electrode sheet includes a first negative electrode active coating. The composite separator includes a positive-side porous active layer and a negative-side porous active layer. The positive-side porous active layer includes a non-adhesive polymer C1. The negative-side porous active layer includes a non-adhesive polymer C2. A compaction density of the first positive electrode active coating is 2.05-3.60 g/cm3. A compaction density of the first negative electrode active coating is 1.40-1.85 g/cm3. Composite of the positive electrode sheet and the composite separator is realized by press-fit processing I. Composite of the negative electrode sheet and the composite separator is realized by press-fit processing II.