PVDF Binder with Acrylic Copolymer for Battery Electrodes
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Solution Overview
Problem
Existing binders for lithium-ion battery electrodes, particularly those containing polyvinylidene fluoride, face issues with adhesion to metal, swelling when in contact with electrolytes, and high viscosity, making them difficult to spread and requiring large amounts, which can lead to electrode detachment and reduced active filler content.
Innovation Solution
A binder comprising a vinylidene fluoride polymer with a high viscosity solution and an acrylic copolymer containing methacrylic acid functional groups, which reduces viscosity and swelling, enhancing adhesion and allowing for a lower binder content, thus increasing active filler capacity and reducing organic solvent use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a polyvinylidene fluoride binder is used to fix material to metal, then adhesion to metal is improved, but viscosity becomes too high making it difficult to spread
Solution Approach 1:
The patent uses a composite binder system combining polyvinylidene fluoride (PVDF) with a small amount of acrylic polymer containing carboxylic acid groups. The PVDF provides strong adhesion to metal surfaces, while the acrylic polymer acts as a dispersant that reduces viscosity and improves processability. This composite approach allows the binder to maintain both high adhesion strength and ease of spreading during electrode manufacturing.
2Strength
If binder content is increased to improve adhesion and prevent detachment, then adhesion is improved, but active filler content decreases
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by incorporating acrylic polymer with carboxylic acid groups alongside PVDF. This compositional modification enables the binder to achieve superior adhesion at lower concentrations, allowing electrode formulations to maintain strong bonding while preserving higher active filler content for improved battery capacity.
3Ease of manufacture
If acrylic polymer is added to reduce viscosity, then ease of spreading is improved, but swelling occurs when in contact with electrolyte
Solution Approach 1:
The patent applies local quality by selecting specific acrylic polymer components with particular functional characteristics - those containing carboxylic acid groups that provide viscosity reduction without excessive swelling. The binder formulation locally optimizes the polymer composition to achieve the right balance between processability and electrochemical stability, ensuring the binder performs reliably in contact with electrolyte while maintaining ease of manufacturing.
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 binder provides improved adhesion, reduced swelling, and lower extractables into the electrolyte, facilitating easier electrode manufacturing and increased battery capacity with a reduced binder content, while being more eco-friendly due to lower organic solvent usage.
Implementation Method 1
an acrylic copolymer containing methacrylic acid functional groups, which reduces viscosity and swelling
Implementation Method 2
The polymer binder makes it possible to provide the cohesion of the deposited layer and the adhesion of the latter to the metal sheet
Implementation Method 3
on contact with the electrolyte, the elastomer will swell and damage the electrode
Data Source
AI summary
The present invention relates to a binder which can be used in a lithium-ion battery, comprising at least one polyvinylidene fluoride and at least one acrylic copolymer including monomers having functional groups which have an affinity for metals or are capable of fixing to the metals. According to the invention, in a characteristic manner, said polyvinylidene fluoride is such that a solution of N-methyl-2-pyrrolidone containing 5 wt % of said polyvinylidene fluoride has a viscosity, measured at 23° C. with an imposed shear rate of 30 rpm, of 125 mPa·s to 1500 mPa·s.