Fluorinated Polymer Binder for Sulfide Battery Electrode Slurries
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Solution Overview
Problem
Existing binders for sulfide-based solid-state batteries have low solubility in solvents, limiting their effectiveness in forming electrodes and electrolyte layers, and do not provide adequate adhesion and flexibility.
Innovation Solution
A polymer binder comprising a vinylidene fluoride unit and a copolymerization unit with specific fluorinated alkyl or alkoxy groups, suitable for use in a low-polarity solvent, is used to create a slurry for sulfide-based solid-state batteries, enhancing solubility, adhesion, and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional binders are used in sulfide-based solid-state batteries, then the electrode structure is maintained, but the solubility in solvents is low and adhesion and flexibility are insufficient
Solution Approach 1:
The patent modifies the chemical structure of the binder polymer by incorporating specific fluorinated monomers (formulae 1 and 2) with adjustable Rf groups. By changing the chemical parameters of the binder - specifically the type and amount of fluorinated comonomers - the patent achieves both high solubility in low-polarity solvents and excellent adhesion to sulfide-based solid electrolytes, resolving the contradiction between manufacturability and reliability
Solution Approach 2:
The patent creates a composite polymer binder system combining vinylidene fluoride (providing base structure and electrochemical stability) with fluorinated comonomers (providing solubility and adhesion properties). This composite material approach allows the binder to simultaneously exhibit multiple desirable properties: solubility in organic solvents, strong adhesion to sulfide electrolytes, and appropriate flexibility for electrode manufacturing
2Ease of operation
If conventional binders are used in sulfide-based solid-state batteries, then the electrode structure is maintained, but the flexibility is insufficient
Solution Approach 1:
The patent adjusts the glass transition temperature (Tg) of the binder by selecting appropriate fluorinated comonomers and controlling their ratio in the copolymer. The Tg can be tuned to achieve optimal flexibility at operating temperatures while maintaining adhesion strength, thereby resolving the contradiction between ease of operation and reliability
3Ease of manufacture
If a polymer with high solubility is designed, then the ease of manufacture is improved, but the adhesion and flexibility may be compromised
Solution Approach 1:
The patent introduces localized polar fluorinated groups (Rf1 and Rf2 in formulae 1 and 2) into specific positions along the polymer chain. These localized polar regions provide strong dipole interactions with sulfide-based solid electrolytes for excellent adhesion, while the overall polymer matrix maintains solubility in low-polarity solvents. This local quality modification resolves the contradiction between manufacturability and reliability
Data Source
AI summary
A binder and a slurry suitable for use in the production of an electrode in a sulfide-based solid-state battery. The binder contains sulfide-based solid electrolyte particles, and is a polymer including a vinylidene fluoride unit and at least one copolymerization unit (A) selected from a monomer unit having a structure represented by formula (1) below and a monomer unit having a structure represented by formula (2) below:wherein Rf1 and Rf2 are each a linear or branched fluorinated alkyl or fluorinated alkoxy group with 1 to 12 carbon atoms, which optionally contains an oxygen atom between carbon-carbon atoms when the number of carbon atoms is 2 or more. The slurry contains sulfide-based solid electrolyte particles, the binder and a solvent. Also disclosed is an electrode including an electrode active material layer formed using the slurry and a lithium-ion secondary solid state battery including the electrode.