Ceramic-Coated Separator Drying for Edge-Uniform High-Speed Production
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Solution Overview
Problem
Existing methods for manufacturing ceramic-coated microporous polyolefin films face challenges such as edge defects and reduced yields due to edge effects in conventional flotation ovens, and the inability to achieve uniform drying at high line speeds, particularly when coating both sides of the film, which limits the width and throughput in producing separators for lithium batteries.
Innovation Solution
A combination of a flotation oven with a stenter approach is used, where the film is restrained in the transverse direction during drying with air knives, minimizing capillary forces and edge effects, allowing for wider widths and higher throughput by applying a ceramic composition to both sides of the polyolefin web.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional flotation oven is used for drying ceramic-coated polyolefin films, then the drying process can be completed, but edge effects occur leading to defects and decreased yields
Solution Approach 1:
The patent applies different drying conditions to different regions of the film by using staggered air knives that provide enhanced drying at the edges compared to the center. This local differentiation compensates for the edge effects that normally cause defects, ensuring uniform drying quality across the entire film surface including the previously problematic edge regions.
Solution Approach 2:
The patent introduces air knives as an intermediary device between the film and the drying environment. These air knives create a controlled air flow field that acts as a mediator to distribute drying forces uniformly across the film, particularly addressing the edge regions where conventional flotation ovens fail to provide adequate drying control.
2Stability of the object's composition
If stenters used in the fabric industry are used for drying, then dimensional stability can be maintained, but line speeds are slower compared to flotation ovens
Solution Approach 1:
The patent merges the dimensional stability control mechanism of stenters (using pins to restrain the film in the transverse direction) with the high-speed drying capability of flotation ovens. This combination allows the film to maintain dimensional stability during drying while achieving higher line speeds than traditional stenter processes, as the air knives provide rapid evaporation without requiring slow, controlled drying.
Solution Approach 2:
The patent uses pneumatic air knives to provide rapid drying through high-velocity air flow. This pneumatic approach enables faster moisture removal compared to conventional thermal drying methods, allowing line speeds to be increased while still maintaining dimensional stability through the mechanical restraint system.
3Device complexity
If the film is not restrained in the transverse direction during drying, then the process is simpler, but capillary forces cause pore collapse and shrinkage
Solution Approach 1:
The patent applies preliminary restraint to the film in the transverse direction using pins before the drying process begins. This preliminary action prevents capillary forces from causing pore collapse and shrinkage during subsequent drying, ensuring the pore structure integrity is maintained throughout the drying process without requiring complex real-time adjustments.
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 method results in freestanding, microporous polyolefin membranes with improved oxidation resistance and high-temperature dimensional stability, enabling wider films and increased production efficiency while maintaining uniformity and reducing defects.
Implementation Method 1
drying with air knives impinging upon the membrane
Implementation Method 2
minimizing capillary forces and edge effects
Data Source
AI summary
The present disclosure relates to a continuous process for coating microporous polyolefin webs with a ceramic composition or slurry, followed by drying at an elevated temperature while being restrained in the transverse direction. Such webs can be used to improve the manufacturability, performance, and safety of energy storage devices such as lithium batteries.