PVDF Binder Composition for Stronger Electrode Collector Adhesion
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Solution Overview
Problem
Vinylidene fluoride polymers used as binders in non-aqueous electrolyte secondary batteries have low adhesive strength to current collectors, which limits the cycle characteristics of the batteries.
Innovation Solution
A binder composition containing a vinylidene fluoride copolymer with a first constituent unit derived from vinylidene fluoride and a second constituent unit that forms an isocyanate group or produces an isocyanate group when heated at 200°C, enhancing adhesion to current collectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a vinylidene fluoride polymer is used as a binder for an electrode, then chemical resistance and electrical stability are improved, but adhesive strength to the current collector deteriorates
Solution Approach 1:
The invention uses a composite binder system comprising a vinylidene fluoride polymer and a polyisocyanate compound. The vinylidene fluoride polymer provides chemical resistance and electrical stability, while the polyisocyanate compound enhances adhesive strength to the current collector. The synergistic combination of these two materials resolves the contradiction by allowing each component to fulfill its strength without compromising the other properties.
Solution Approach 2:
The invention changes the chemical composition parameters of the binder by introducing a polyisocyanate compound with specific functional groups (isocyanate groups) that react with the vinylidene fluoride polymer. This parameter change in composition enables the binder to achieve both high chemical resistance/electrical stability from the vinylidene fluoride polymer and high adhesive strength from the polyisocyanate compound's reactive functional groups.
2Strength
If a curing agent is added to enhance adhesive strength, then adhesive strength is improved, but device complexity and manufacturing process complexity increase
Solution Approach 1:
The invention merges the binder and curing agent into a single integrated binder composition. The polyisocyanate compound serves dual functions as both the binder component and the curing agent, eliminating the need for separate addition and mixing operations. This merging reduces device complexity and streamlines the manufacturing process while maintaining enhanced adhesive strength.
Solution Approach 2:
The polyisocyanate compound in the binder composition exhibits self-curing capability through its reactive isocyanate groups that can react with hydroxyl groups or water present in the electrode mixture or on the current collector surface. This self-service characteristic eliminates the need for external curing agents or complex curing processes, thereby reducing manufacturing complexity while achieving high adhesive strength.
3Strength
If a polyisocyanate compound is used as a curing agent, then adhesive strength is improved, but gelling during storage may occur
Solution Approach 1:
The invention uses a controlled amount of polyisocyanate compound in the binder composition, optimizing the ratio between the vinylidene fluoride polymer and polyisocyanate compound. By using a partial amount of the reactive polyisocyanate compound rather than excessive amounts, the binder achieves sufficient adhesive strength while minimizing the risk of premature gelling during storage. This partial action approach balances reactivity with storage stability.
Solution Approach 2:
The polyisocyanate compound is pre-incorporated into the binder composition in a stable form that does not immediately react. The binder composition is designed to remain stable during storage, with the polyisocyanate compound's reactive groups becoming active only during the electrode formation process or initial heating treatment. This preliminary preparation allows the binder to maintain adhesive potential without gelling during storage.
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 binder composition significantly improves the adhesive strength of the electrode mixture layer to current collectors, enhancing the cycle characteristics and facilitating mass production by eliminating the need for mixing operations, while preventing gelling during storage.
Implementation Method 1
a second constituent unit containing an isocyanate group or having a structure that produces an isocyanate group when heated at 200° C. for 1 hour
Data Source
AI summary
The present invention is to provide a binder composition of a non-aqueous electrolyte secondary battery, which contains a vinylidene fluoride polymer and is capable of further enhancing adhesive strength of the electrode mixture layer to a surface of a current collector. The above objective can be achieved by a binder composition of a non-aqueous electrolyte secondary battery, the binder composition comprising a vinylidene fluoride copolymer for a binder of a non-aqueous electrolyte secondary battery, the vinylidene fluoride copolymer containing: a first constituent unit derived from vinylidene fluoride, and a second constituent unit containing an isocyanate group or having a structure that produces an isocyanate group when heated at 200° C. for 1 hour. This binder composition can be used in a mixture for producing an electrode for a non-aqueous electrolyte secondary battery, an electrode for a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery.