Fluorinated Block Copolymer Separator Coating for Lithium Batteries
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Solution Overview
Problem
Lithium batteries face challenges in providing a separator coating with strong adhesion to the base material and minimal swelling when exposed to electrolyte solvents, which affects long-term battery performance.
Innovation Solution
A fluorinated block copolymer with alternating hard and soft blocks, comprising recurring units from vinylidenefluoride (VDF) and perhalogenated monomers, is used to create a coating for the separator, ensuring good adhesion and reduced swelling in electrolyte solvents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a coating is applied to the separator base material to improve adhesion, then adhesion strength is improved, but swelling occurs when contacted with electrolyte solvent
Solution Approach 1:
The patent changes the chemical composition parameters of the coating material by using a fluorinated copolymer with specific monomer ratios (VDF 45-85 mol%, HFP 15-55 mol%). This parameter optimization allows the coating to achieve both strong adhesion to the separator base material and resistance to swelling in electrolyte solvents, resolving the contradiction between adhesion strength and swelling resistance.
Solution Approach 2:
The patent employs a composite fluorinated copolymer material combining vinylidenefluoride (VDF) and hexafluoropropylene (HFP) monomers in specific proportions. This composite material structure provides both the adhesion properties needed for strong bonding to the separator and the chemical stability required to minimize swelling when exposed to electrolyte solvents, thus resolving the technical contradiction.
2Strength
If HFP monomer content is increased to improve adhesion, then adhesion is improved, but swelling resistance deteriorates
Solution Approach 1:
The patent optimizes the HFP monomer content parameter within a specific range (15-55 mol%, preferably 20-50 mol%). This parameter control ensures that the coating has sufficient adhesion to the separator base material while maintaining adequate resistance to swelling in electrolyte solvents. The balanced composition resolves the contradiction between improving adhesion through higher HFP content and maintaining swelling resistance.
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 fluorinated block copolymer coating achieves excellent adhesion to the separator base material while minimizing swelling, thereby enhancing the long-term performance of lithium batteries.
Implementation Method 1
The fluorinated block copolymer coating achieves excellent adhesion to the separator base material
Implementation Method 2
minimizing swelling when immersed in the electrolyte solvent
Data Source
AI summary
Provided are fluorinated block copolymers comprising alternating hard blocks and soft blocks, wherein both said hard and soft blocks comprise vinylidenfluoride (VDF). Also provided is the use of said block copolymers in applications for lithium batteries including an electrochemical cell and a separator for an electrochemical cell which is coated with a composition comprising the fluorinated block copolymers. Further provided is a process for the manufacture of the separator.