PVDF Copolymer Binder for Flexible Battery Adhesion
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Solution Overview
Problem
Existing methods for manufacturing electrodes and separators for electrochemical devices, such as batteries, face challenges in achieving both good adhesion to current collectors and flexibility, especially in flexible batteries, where components must withstand bending while maintaining adhesion and chemical stability during charging and discharging cycles.
Innovation Solution
A composition comprising a semi-crystalline fluoropolymer with recurring units derived from vinylidene fluoride and a hydrophilic (meth)acrylic monomer, combined with another fluoropolymer containing vinylidene fluoride and a fluorinated monomer, is used to create electrodes and separators with improved adhesion and flexibility, utilizing a non-aqueous solvent-based process for easier coating and drying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a fluoropolymer binder is used to ensure good adhesion of electrodes to current collectors, then adhesion is improved, but the flexibility and ability to withstand bending is reduced
Solution Approach 1:
The patent uses a composite binder system combining PVDF (polyvinylidene fluoride) with a small amount of hydrophilic polymer (0.1-5 wt%). This composite approach leverages the strong adhesion properties of PVDF while the hydrophilic polymer component provides flexibility and bend resistance, resolving the contradiction between adhesion strength and flexibility.
Solution Approach 2:
The patent modifies the binder composition by introducing hydrophilic polymers with specific molecular weights and functional groups. This parameter change transforms the binder's mechanical properties, enabling it to maintain both strong adhesion and flexibility under bending conditions without sacrificing electrochemical performance.
2Reliability
If PVDF is used as the binder to maintain thermal stability and mechanical properties, then reliability is improved, but the slurry viscosity is high making manufacturing difficult
Solution Approach 1:
The patent introduces hydrophilic polymers with specific molecular weights (10,000-1,000,000 g/mol) and functional groups that interact with PVDF to modify slurry rheology. This parameter change reduces slurry viscosity while preserving PVDF's thermal stability, facilitating easier coating and manufacturing processes.
Solution Approach 2:
The hydrophilic polymer acts as an intermediary substance that modifies the interaction between PVDF particles and the solvent in the slurry. This intermediary reduces viscosity and improves flow characteristics without compromising the thermal and mechanical stability provided by PVDF, making the slurry easier to process.
3Ease of manufacture
If electrode slurry with low viscosity is used to ease manufacturing, then ease of manufacture is improved, but adhesion quality may be compromised
Solution Approach 1:
The patent carefully selects hydrophilic polymers with specific molecular weights and concentrations (0.1-5 wt%) that reduce slurry viscosity to facilitate manufacturing while maintaining optimal adhesion quality. The parameter optimization ensures that the binder forms strong bonds during the drying process despite the lower viscosity of the applied slurry.
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 solution provides electrodes and separators with enhanced flexibility and adhesion to current collectors, facilitating easier manufacturing and maintaining performance under bending stress, while maintaining the thermal stability and mechanical properties of vinylidene fluoride polymers.
Implementation Method 1
the role of the organic solvent is typically to dissolve the fluoropolymer in order to bind the electro-active material particles to each other and to the metal collector upon evaporation of the organic solvent. The fluoropolymer binder should properly bind the electro-active material particles to each other and to the metal collector
Implementation Method 2
techniques for manufacturing either positive or negative electrodes and also for coating separators involve the use of organic solvents for dissolving the fluoropolymer
Implementation Method 3
the role of the organic solvent is typically to dissolve the fluoropolymer in order to bind the electro-active material particles to each other and to the metal collector upon evaporation of the organic solvent
Data Source
AI summary
The present disclosure pertains to vinylidene fluoride copolymers comprising recurring units derived from hydrophilic (meth)acrylic monomers and fluoro monomers compositions, and to their use in the manufacturing of battery components, such as membrane separators and electrode binders, to said battery components and to electrochemical devices comprising said components. Processes of making said copolymers and electrodes and separators including the copolymers are also described.