Secondary Battery Mixture Sheet Using Large Particles for PTFE Fibrillation
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Solution Overview
Problem
Existing methods for producing secondary battery mixtures using polytetrafluoroethylene (PTFE) as a binder resin face challenges such as insufficient fibrillation, leading to suboptimal physical strength and battery performance, and are plagued by issues like solvent residue and chemical reactions that degrade battery materials.
Innovation Solution
Incorporating particles with a size of 20 μm or more into the secondary battery mixture, along with a fibrillatable PTFE resin that forms fibrils under shear stress, to enhance fibrillation efficiency and produce a mixture sheet with improved physical properties without the need for solvents, thereby avoiding the drawbacks of conventional methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polytetrafluoroethylene is fibrillated by subjecting a mixture to high shear treatment, then the binder forms fibrils, but the fibrillation is insufficient leading to suboptimal physical strength and battery performance
Solution Approach 1:
The patent changes the particle size parameter of the active material to 20 μm or more, which serves as abrasives during mixing to enhance fibrillation of the PTFE binder. This parameter change resolves the contradiction by improving fibrillation efficiency (manufacturing precision) while achieving sufficient physical strength through the combined effect of fibrils and large particles.
2Reliability
If conventional methods are used to produce secondary battery mixtures, then the process is established, but solvent residue and chemical reactions occur that degrade battery materials
Solution Approach 1:
The patent extracts and eliminates the solvent component from the conventional slurry coating process. By using a solvent-free mixing method where PTFE fibrillates directly during high-shear mixing with large particles as abrasives, the harmful solvent residue and associated chemical reactions are completely removed, improving battery material stability.
3Strength
If particles with size of 20 μm or more are incorporated into the mixture, then fibrillation efficiency is enhanced and physical properties are improved, but the mixture composition becomes more complex
Solution Approach 1:
The patent assigns multiple functions to the large particles (20 μm or more): they serve as active material, act as abrasives to enhance fibrillation, and function as structural reinforcement. This multi-functionality resolves the contradiction by improving strength and toughness without requiring additional separate components, thus not increasing mixture composition complexity.
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 results in a secondary battery mixture and sheet with enhanced strength, toughness, and reduced resistance, while maintaining high productivity and avoiding the pitfalls of solvent use, such as degradation of battery materials.
Implementation Method 1
fibrillatable PTFE resin that forms fibrils under shear stress
Data Source
AI summary
Provided are a secondary battery mixture that has good properties in terms of strength and battery performance, a secondary battery mixture sheet containing the mixture, and a secondary battery using the secondary battery mixture sheet. The secondary battery mixture includes a fibrillatable resin and particles A having a particle size of 20 μm or more. The secondary battery mixture contains on average 80 or more of the particles A per 1 mm3 of the mixture.