Battery Separator Coating for Adhesion and Winding Stability
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Solution Overview
Problem
Conventional separators for electricity storage devices face issues such as uneven adhesive strength, insufficient binding strength, powder flaking during production, and reduced productivity, particularly in high-density modularization of non-aqueous secondary batteries, necessitating improvements in output characteristics and cycle characteristics.
Innovation Solution
A separator comprising a polyolefin microporous membrane with a covering layer containing an inorganic filler and a particulate thermoplastic polymer, where the particulate polymer protrudes from the inorganic filler, and the covering layer has a specific coefficient of static friction, gradient shape, and controlled distribution of particulate polymers to enhance adhesive strength and prevent misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a covering layer containing thermoplastic polymer is arranged on the substrate to improve adhesion between the separator and electrodes, then adhesive strength is improved, but the separator exhibits poor gripping performance and winding misalignment during production
Solution Approach 1:
The patent applies local quality by creating a covering layer with non-uniform distribution of thermoplastic polymer particles, where the particle density and protrusion height vary across different regions. This allows the separator to have different gripping performances in different areas - regions with lower particle density provide better gripping performance for production handling, while regions with higher particle density provide stronger adhesion to electrodes, thus resolving the contradiction between adhesive strength and gripping performance
Solution Approach 2:
The patent changes the physical parameters of the thermoplastic polymer particles, specifically controlling their volume average particle size to be 1 μm or more and 10 μm or less, and controlling the protrusion height to be 0.1 μm or more and 3 μm or less. These parameter optimizations enable the particles to provide sufficient adhesion while maintaining appropriate gripping performance during production, resolving the contradiction between adhesive strength and ease of manufacture
2Quantity of substance
If the volume of the electricity storage device is reduced by hot pressing to increase capacity, then energy density is improved, but the separator and electrodes require additional affixing processes to maintain volume
Solution Approach 1:
The patent applies self-service by designing the covering layer with thermoplastic polymer particles that automatically provide both volume maintenance and electrode affixing functions through their inherent adhesive properties when heated during hot pressing. The particles soften and bond the separator to electrodes without requiring additional external affixing processes, thus maintaining energy density while simplifying the production process and reducing device complexity
3Ease of manufacture
If conventional separators are used without protruding polymer particles, then production is simpler, but adhesive strength is insufficient and powder flaking occurs during production
Solution Approach 1:
The patent applies composite materials by combining inorganic filler particles with thermoplastic polymer particles in the covering layer. The inorganic filler provides structural stability and prevents powder flaking during production, while the thermoplastic polymer particles provide adhesive strength to bond the separator to electrodes. This composite structure maintains production simplicity while simultaneously improving adhesive strength and preventing powder flaking
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 solution improves adhesive strength with electrodes, reduces thermal shrinkage, enhances cycle characteristics, and increases productivity by preventing winding misalignment and improving gripping performance during production.
Implementation Method 1
a covering layer arranged on at least one surface of the substrate, wherein the covering layer comprises an inorganic filler and a particulate thermoplastic polymer
Implementation Method 2
The separator has the function of preventing direct contact between the positive electrode and the negative electrode and allowing ions to permeate through the electrolyte solution held in the micropores thereof
Data Source
AI summary
The present invention provides a separator for power storage devices, the separator comprising a base material 10 which is a polyolefin microporous membrane that contains a polyolefin as a main component, and a cover layer 20 which is arranged on at least one surface of the base material 10. With respect to this separator for power storage devices, the cover layer 20 contains an inorganic filler 1 and a thermoplastic polymer; the thermoplastic polymer forms particulate polymers 2 that protrude from an inorganic filler portion L1; and the coefficient of static friction of the cover layer 20 is 0.40 to 0.60.