Multi-Fluoropolymer Binder Composition for Adhesive Battery Electrodes
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Solution Overview
Problem
Existing binders in secondary batteries have low adhesion and require large amounts to ensure effective adhesion of electrode plates, which hinders energy density increase and cycling performance.
Innovation Solution
A binder composition comprising a first fluoropolymer with a weight-average molecular weight of 3000000-10000000, a second fluoropolymer with a weight-average molecular weight of 600000-1100000, and a third fluoropolymer with a weight-average molecular weight of 5000-150000, which provides sufficient adhesion even when added in small amounts, improving cycling performance and flexibility of the electrode plate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If existing binders are used to ensure adhesion of electrode plates, then adhesion force is sufficient, but large amounts of binder are required which hinders energy density increase
Solution Approach 1:
The patent applies parameter changes by carefully controlling the weight-average molecular weight of PVDF within 1000000-5000000 range and limiting crystallinity to 40% or less. These parameter optimizations enable the binder to achieve sufficient adhesion force with reduced quantity, directly resolving the contradiction between adhesion strength and binder amount required for energy density improvement
Solution Approach 2:
The patent creates a composite binder system by combining PVDF with specific additives including polyacrylonitrile (PAN) at 1-50 parts by weight per 100 parts PVDF, and hydrophilic polymers. This composite approach enhances adhesion efficiency, allowing smaller amounts of binder composition to achieve the required adhesion force, thereby increasing energy density
2Strength
If large amounts of binder are added to improve adhesion, then adhesion force increases, but energy density decreases
Solution Approach 1:
By optimizing PVDF molecular weight to 1000000-5000000 and controlling crystallinity at 40% or less, the patent achieves maximum adhesion efficiency per unit mass of binder. This allows minimal binder quantity to be used while maintaining sufficient adhesion, thereby preserving energy density
Solution Approach 2:
The patent introduces hydrophilic polymers and PAN that can form hydrogen bonding networks, creating alternative adhesion mechanisms that replicate and enhance the binding function of traditional fluoropolymer binders with higher efficiency, reducing the overall binder mass required
3Reliability
If binder composition is optimized for adhesion, then cycling performance improves, but processability may be affected
Solution Approach 1:
The patent controls PVDF crystallinity at 40% or less through specific processing conditions and additive selection. This crystallinity control maintains good processability and slurry formation while ensuring sufficient adhesion force for improved cycling performance, balancing both requirements
Solution Approach 2:
The patent uses PAN and hydrophilic polymers as intermediary substances that facilitate both processing and adhesion. These intermediaries improve slurry homogeneity and coating uniformity during manufacturing while simultaneously enhancing electrode plate adhesion, thus improving cycling performance without compromising processability
Data Source
AI summary
This application provides a binder composition. The binder composition includes a first fluoropolymer and a second fluoropolymer, where the first fluoropolymer includes polyvinylidene fluoride with a weight-average molecular weight of 5000000-9000000, and a weight-average molecular weight of the second fluoropolymer is not greater than 600000. Featuring good processability, this binder composition, even added in small amounts, can provide electrode plates with great adhesion force and improve the cycling performance of a battery.