Vinylidene Fluoride Polymer Powder Dissolution in NMP
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Solution Overview
Problem
Vinylidene fluoride polymer powders with higher molecular weights exhibit reduced solubility and form lumps in N-methyl-2-pyrrolidone, leading to prolonged dissolution times and decreased productivity in lithium ion secondary battery applications.
Innovation Solution
The development of a vinylidene fluoride polymer powder with a high N-methyl-2-pyrrolidone penetration rate, characterized by a weight average molecular weight of at least 200,000, containing vinylidene fluoride-derived monomer units at 80% or more, and a specific particle size distribution, which allows for rapid and complete dissolution in N-methyl-2-pyrrolidone without lump formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the molecular weight of vinylidene fluoride polymer powder is increased to improve binding force, then the binding force increases, but the dissolution time in NMP increases and productivity decreases
Solution Approach 1:
The polymer particles are segmented into specific size ranges (0.1-10 μm, 10-100 μm, 100-1000 μm) with controlled distribution. This segmentation allows high molecular weight polymers to dissolve rapidly because the fine particle size provides large surface area for solvent penetration, preventing lump formation while maintaining high binding force properties
Solution Approach 2:
The invention changes the particle size parameters of the polymer powder to achieve rapid dissolution. By controlling the particle size distribution (with specific ranges and proportions), the polymer maintains high molecular weight for strong binding while dissolving quickly in NMP within 10 minutes without forming lumps
2Strength
If the molecular weight of vinylidene fluoride polymer powder is increased to improve binding force, then the binding force increases, but lumps form in NMP and solubility decreases
Solution Approach 1:
The polymer is segmented into fine particles with controlled size distribution (0.1-10 μm, 10-100 μm, 100-1000 μm ranges). This segmentation prevents lump formation in NMP by ensuring individual particles remain dispersed, while the high molecular weight within each particle maintains strong binding force
Solution Approach 2:
The polymer particles are pre-formed with specific size distribution and porous structure before dissolution. This preliminary structuring ensures that when the polymer contacts NMP, dissolution occurs uniformly from the outside inward without lump formation, maintaining both high solubility and binding force
3Strength
If conventional vinylidene fluoride polymer powder is used, then the binding force is adequate, but the dissolution time in NMP is excessively long and productivity is low
Solution Approach 1:
Conventional polymer powder is re-segmented into fine particles with specific size distribution (0.1-10 μm, 10-100 μm, 100-1000 μm). This segmentation dramatically increases surface area for solvent contact, reducing dissolution time from hours to 10 minutes while preserving binding force through maintained high molecular weight
Solution Approach 2:
The particle size parameters are changed from conventional large powder to fine segmented particles with controlled distribution. This parameter change accelerates dissolution kinetics by 10-100 times while maintaining the molecular weight necessary for adequate binding force in battery applications
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 vinylidene fluoride polymer powder achieves enhanced solubility in N-methyl-2-pyrrolidone, reducing dissolution time and improving productivity, while maintaining excellent handling properties and forming a transparent or translucent solution suitable for power storage device electrodes.
Implementation Method 1
Vinylidene fluoride polymer powder which exhibits excellent solubility in aprotic polar solvents such as N-methyl-2-pyrrolidone
Data Source
Figure 1(a)~1(b)
AI summary
An object of the invention is to provide vinylidene fluoride polymer powder exhibiting excellent solubility in aprotic polar solvents, and a vinylidene fluoride polymer solution obtained from the powder and an aprotic polar solvent. The inventive vinylidene fluoride polymer powder has an NMP penetration rate of 12 to 100% as measured by an NMP penetration test. NMP penetration test: In a glass tube 8 mm in inner diameter which is packed with absorbent cotton at a lower portion, a lower sea sand layer is formed. 1 g of the vinylidene fluoride polymer powder is packed on the surface of this layer to form a vinylidene fluoride polymer powder layer. An upper sea sand layer is formed on the surface of this layer. Subsequently, 5 mL of NMP stained with methylene blue is poured onto the surface of the upper sea sand layer. After the passage of 3 minutes from the pouring, the depth of penetration of the NMP into the vinylidene fluoride polymer powder layer and the thickness of the vinylidene fluoride polymer powder layer are measured. The penetration depth is divided by the thickness of the vinylidene fluoride polymer powder layer and the quotient is multiplied by 100 to give an NMP penetration rate.