Composite Separator Coating With Aqueous Slurry Wettability Control
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Solution Overview
Problem
Current methods for manufacturing separators for electrochemical devices using organic solvent-based slurries pose safety hazards, are environmentally unfriendly, and have low wettability issues on polyolefin-based substrates, which can lead to thermal contraction and short circuits, compromising safety and efficiency.
Innovation Solution
A method involving an aqueous slurry with inorganic particles, a binder polymer, and an aqueous medium is used to form an organic-inorganic composite porous coating layer on a porous polymer substrate, with controlled capillary number, viscosity, coating velocity, and surface tension to enhance wettability and safety, employing additives like hydrophilic surfactants and thickening agents to achieve optimal coating properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an organic solvent-based slurry is used for coating the separator, then the coating process can proceed, but safety hazards and environmental pollution occur
Solution Approach 1:
The patent changes the fundamental parameter of the slurry medium from organic solvent-based to aqueous-based. This substitution eliminates the safety hazards and environmental pollution associated with organic solvents while maintaining the coating process feasibility through careful control of other parameters such as viscosity and surface tension of the aqueous slurry.
Solution Approach 2:
The patent employs a disposable aqueous slurry system that can be easily prepared and discarded without environmental contamination concerns. The aqueous-based formulation allows for simple waste disposal compared to organic solvent systems, reducing both safety risks and environmental impact while maintaining manufacturing efficiency.
2Object-affected harmful factors
If an aqueous slurry is used for coating the separator, then safety and environmental friendliness are improved, but wettability on polyolefin-based substrate is poor
Solution Approach 1:
The patent introduces surfactants as intermediary substances in the aqueous slurry formulation. These surfactants act as mediators between the aqueous slurry and the hydrophobic polyolefin substrate, reducing surface tension and improving wettability. This allows the aqueous slurry to effectively coat the substrate without compromising safety or environmental benefits.
Solution Approach 2:
The patent adjusts critical parameters of the aqueous slurry including viscosity, surface tension, and capillary number to optimize wettability on polyolefin substrates. By carefully controlling these parameters, the aqueous slurry achieves proper penetration and adhesion to the substrate while maintaining the safety and environmental advantages of water-based formulation.
3Manufacturing precision
If the capillary number is not properly controlled, then coating uniformity deteriorates, but controlling it precisely increases process complexity
Solution Approach 1:
The patent establishes a specific range for the capillary number (0.01 to 10) as a key control parameter. By defining this optimal range, the patent simplifies the coating process - operators only need to ensure the capillary number falls within this range rather than precisely controlling multiple independent variables. This approach maintains coating uniformity while reducing overall process complexity.
Solution Approach 2:
The patent makes the capillary number a universal control parameter that integrates multiple aspects of the coating process (viscosity, surface tension, coating speed). By focusing on this single multi-functional parameter, the patent simplifies process control while ensuring coating quality, as adjusting the capillary number simultaneously affects multiple coating characteristics in a coordinated manner.
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
This approach ensures improved safety and economic efficiency by facilitating better wetting and coating of the substrate, reducing the risk of thermal runaway and short circuits, while maintaining high performance and environmental sustainability.
Implementation Method 1
coating the aqueous slurry on at least one surface of a porous polymer substrate to form an organic-inorganic composite porous coating layer wherein capillary number of the aqueous slurry is from 0.3 to 65
Implementation Method 2
a separator with a porous organic-inorganic coating layer formed by coating a mixture of excess inorganic particles and a binder polymer on at least one surface of a porous polymer substrate having plural pores was proposed. The inorganic particles included in the porous organic-inorganic coating layer have good heat resistance, thereby preventing a short circuit between a positive electrode (or cathode) and a negative electrode (or anode) when an electrochemical device is overheated.
Data Source
AI summary
A preparation method of a separator according to the present disclosure includes preparing an aqueous slurry including inorganic particles, a binder polymer, and an aqueous medium, and coating the aqueous slurry on at least one surface of a porous polymer substrate to form an organic-inorganic composite porous coating layer, wherein capillary number of the aqueous slurry has a range between 0.3 and 65.