PVdF Electrode Binder Composition With Stable Slurry Viscosity
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Solution Overview
Problem
Existing electrode binders face challenges in providing excellent electrolytic solution swelling resistance, adhesion to metal foils, flexibility, and viscosity stability in secondary batteries.
Innovation Solution
A composition comprising polyvinylidene fluoride (PVdF) with a specific content of vinylidene fluoride and pentenoic acid units, along with a vinylidene fluoride polymer, is used to create an electrode mixture that ensures strong adhesion, flexibility, and resistance to electrolyte swelling while maintaining stable viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional vinylidene fluoride-based binder is used, then adhesion to metal foil is achieved, but electrolytic solution swelling resistance is insufficient
Solution Approach 1:
The patent uses a composite binder system combining polyvinylidene fluoride (PVdF) with a copolymer containing carboxylic acid groups. This composite approach allows the PVdF component to provide electrolytic solution swelling resistance while the copolymer with carboxylic acid groups provides strong adhesion to the metal foil current collector, thus resolving the contradiction between these two properties.
Solution Approach 2:
The binder composition is designed with different functional components distributed to perform specific local functions: PVdF provides bulk swelling resistance, while the copolymer with carboxylic acid groups localizes at the metal foil interface to provide adhesion. This local quality differentiation allows simultaneous optimization of both swelling resistance and adhesion.
2Stability of the object's composition
If binder composition is optimized for adhesion, then flexibility is improved, but viscosity increases
Solution Approach 1:
The patent carefully controls the carboxylic acid content in the copolymer within a specific range (0.1-10 mol%) to optimize the balance between flexibility and viscosity. By adjusting this compositional parameter, the binder achieves sufficient flexibility for electrode formation while preventing excessive viscosity increase that would hinder processing.
3Strength
If hydrophilic monomer content is increased to improve adhesion, then electrolytic solution swelling resistance decreases
Solution Approach 1:
The patent employs a composite binder where PVdF (hydrophobic) and copolymer with carboxylic acid groups (hydrophilic) work together. The PVdF component compensates for the reduced swelling resistance introduced by the hydrophilic copolymer, while the copolymer provides the necessary adhesion. This composite approach allows utilization of both hydrophobic and hydrophilic properties.
Solution Approach 2:
The hydrophilic carboxylic acid groups are concentrated at the metal foil interface where they provide adhesion, while the bulk PVdF matrix maintains electrolytic solution swelling resistance. This spatial separation of functional properties allows simultaneous achievement of both adhesion and swelling resistance.
Data Source
AI summary
Provided is a composition comprising: a polyvinylidene fluoride (A); and a vinylidene fluoride polymer (B) excluding the polyvinylidene fluoride (A), wherein the polyvinylidene fluoride (A) comprises vinylidene fluoride unit and a pentenoic acid unit represented by formula (1): CH2=CH-(CH)2-COOY wherein Y represents at least one selected from the group consisting of an inorganic cation and an organic cation, a content of vinylidene fluoride unit of the polyvinylidene fluoride (A) is 95.0 to 99.99 mol% based on all monomer units of the polyvinylidene fluoride (A), and a content of the pentenoic acid unit of the polyvinylidene fluoride (A) is 0.01 to 5.0 mol% based on all monomer units of the polyvinylidene fluoride (A) .