Fluorinated Electrode Primer Layer for Stable Current Collector Adhesion
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Solution Overview
Problem
Secondary batteries using electrodes with fluorinated or hydrocarbon-type polymers as binders suffer from inadequate adhesion to current collectors, leading to poor charge-discharge cycle characteristics and discharge rate characteristics due to the deterioration of primer coating layers made from polyurethane or epoxy resins during battery operation.
Innovation Solution
A primer layer is formed using a fluorinated copolymer with units based on tetrafluoroethylene or chlorotrifluoroethylene and ethylene, hexafluoropropylene, or perfluoro(alkyl vinyl ether), which has adhesive functional groups that can react with hydroxy groups or form hydrogen bonds, and has a melting point of at least 150°C, enhancing the adhesion between the current collector and the electrode active material layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a polyurethane resin or epoxy resin is used as a primer coating layer, then the adhesion of the electrode composite to the current collector surface is improved, but the primer coating layer deteriorates during charge and discharge, causing adhesion to be lost
Solution Approach 1:
The invention changes the chemical parameters of the primer coating layer by using a fluorinated copolymer with specific monomer units (tetrafluoroethylene, chlorotrifluoroethylene, ethylene, hexafluoropropylene, or perfluoro(alkyl vinyl ether)) and a melting point of at least 150°C. This parameter change enables the primer to maintain both adhesion and stability during charge-discharge cycles, resolving the contradiction between initial adhesion improvement and long-term reliability.
Solution Approach 2:
The invention uses a composite fluorinated copolymer structure combining multiple monomer units with specific properties. The copolymer contains units that provide high melting point (structural stability) and units with adhesive functional groups (adhesion capability). This composite material approach allows the primer to simultaneously achieve strong adhesion and resistance to deterioration during battery operation.
2Ease of manufacture
If a fluorinated polymer or hydrocarbon-type polymer is used as a binder, then the electrode composite can be formed, but the adhesion to the current collector surface is inadequate
Solution Approach 1:
The fluorinated copolymer primer coating layer acts as an intermediary between the current collector surface and the electrode composite containing fluorinated or hydrocarbon-type polymer binders. The primer provides adhesive functional groups that bond to the current collector, while its high melting point structure supports the electrode composite, enabling both ease of manufacture and adequate adhesion.
3Productivity
If a binder containing fluorinated polymer or hydrocarbon-type polymer is used, then the electrode can be produced, but sufficient charge-discharge cycle characteristics and discharge rate characteristics cannot be obtained
Solution Approach 1:
The invention applies a fluorinated copolymer primer coating layer to the current collector surface before forming the electrode composite. This preliminary action creates a stable, high-melting-point foundation that prevents deterioration during subsequent charge-discharge cycles, enabling the electrode to achieve sufficient cycle characteristics and discharge rate characteristics while maintaining productivity.
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 proposed solution results in excellent charge-discharge cycle characteristics and discharge rate characteristics by maintaining the adhesion and stability of the electrode composite to the current collector, improving the overall performance of the secondary battery.
Implementation Method 1
adhesive functional groups that can react with hydroxy groups or can form hydrogen bonds
Data Source
AI summary
To provide a secondary battery having excellent charge-discharge cycle characteristics (capacity retention rate) and discharge rate characteristics (discharge capacity ratio), as well as a primer for a power storage device electrode, a composition for forming a primer layer and an electrode for a power storage device, to obtain such a secondary battery. A primer for a power storage device electrode, to form a primer layer between a current collector and an electrode active material layer, said primer for a power storage device electrode, containing a fluorinated copolymer which has units based on tetrafluoroethylene or chlorotrifluoroethylene and units based on ethylene, hexafluoropropylene or a perfluoro(alkyl vinyl ether), but does not substantially have units based on vinylidene fluoride, and which has adhesive functional groups that can react with hydroxy groups or can form hydrogen bonds.