VDF-HFP Binder for Solid-State Battery Negative Electrode
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Solution Overview
Problem
Existing methods for manufacturing negative electrodes for solid-state batteries face challenges in preventing sulfide solid electrolyte deterioration, ensuring sufficient adhesive force between the current collector and electrode layer, and suppressing capacity deterioration during initial charging.
Innovation Solution
A method involving a negative electrode slurry with a binder composed of a vinylidene fluoride (VDF) and hexafluoropropylene (HFP) copolymer, using butyl butyrate as the solvent, and optimizing the HFP molar ratio to 10-25% to prevent sulfide solid electrolyte deterioration and ensure strong adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If N-methylpyrrolidone is used as a solvent to dissolve polyvinylidene fluoride binder, then the binder solubility is improved, but the lithium ion conductivity of the sulfide solid electrolyte decreases due to chemical reaction
Solution Approach 1:
The patent extracts and removes the problematic TFE component from the binder composition, using only VDF and HFP monomers. This elimination of the harmful TFE unit prevents the chemical reaction with sulfide solid electrolyte while maintaining binder solubility in esters like butyl butyrate, thus resolving the contradiction between binder solubility and electrolyte conductivity preservation
Solution Approach 2:
The patent changes the chemical composition parameters of the binder by specifying a copolymer containing VDF and HFP in a molar ratio of 80:20 to 95:5, with TFE content of 5 mol% or less (preferably 0-2 mol%). This parameter adjustment maintains the binder's solubility properties while eliminating the harmful reactivity with sulfide solid electrolyte, thereby preserving lithium ion conductivity
2Stability of the object's composition
If polyvinylidene fluoride or three-component copolymer binder is used, then the binder can be dissolved in appropriate solvents, but the adhesive force between current collector and electrode layer becomes insufficient
Solution Approach 1:
The patent optimizes the binder composition parameters by using a two-component copolymer of VDF and HFP with specific molar ratios (VDF:HFP = 95:5 to 80:20). This compositional parameter change enhances the adhesive properties of the binder while maintaining its solubility in ester-based solvents, thereby resolving the contradiction between solubility and adhesive strength
Solution Approach 2:
The patent creates a composite binder system using copolymerization of VDF and HFP monomers, where the specific ratio of these two components produces a material with both good solubility in esters and enhanced adhesive force. This composite approach allows simultaneous achievement of solubility and adhesion that neither pure PVDF nor three-component copolymers could provide
3Stability of the object's composition
If three-component copolymer binder containing TFE is used, then the binder can be dissolved in solvents, but the battery capacity decreases during initial charging due to binder decomposition
Solution Approach 1:
The patent extracts and eliminates the TFE component from the binder composition, using only VDF and HFP monomers. This removal of the problematic TFE unit prevents its decomposition and reaction with lithium ions during initial charging, thereby preventing capacity loss while maintaining binder solubility through the VDF-HFP copolymer system
Solution Approach 2:
The patent changes the binder composition parameters by specifying TFE content of 5 mol% or less (preferably 0-2 mol%) and using a two-component VDF-HFP copolymer system. This parameter modification eliminates the source of capacity loss during initial charging while preserving the necessary solubility properties for slurry preparation
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
This approach effectively prevents sulfide solid electrolyte deterioration, secures a sufficient adhesive force between the current collector and negative electrode layer, and suppresses capacity deterioration during initial charging, enhancing the performance of solid-state batteries.
Implementation Method 1
securing a sufficient adhesive force between a current collector and a negative electrode layer
Implementation Method 2
mixing a negative electrode active material, a sulfide solid electrolyte, a binder, and a solvent with each other to prepare a negative electrode slurry
Implementation Method 3
drying the applied negative electrode slurry
Data Source
AI summary
Provided is a method of manufacturing a negative electrode for a solid-state battery, the method including: a step of mixing a negative electrode active material, a sulfide solid electrolyte, a binder, and a solvent with each other to prepare a negative electrode slurry; a step of applying the prepared negative electrode slurry to a surface of a solid electrolyte layer of the solid-state battery or a substrate of the negative electrode; and a step of drying the applied negative electrode slurry. In this method, the solvent is butyl butyrate, and the binder is a copolymer containing a vinylidene fluoride (VDF) monomer unit and a hexafluoropropylene (HFP) monomer unit, in which a molar ratio of the HFP monomer unit to a total amount of the VDF monomer unit and the HFP monomer unit is 10% to 25%.