Secondary Battery Binder Composition for Dense, Uniform Electrodes
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Solution Overview
Problem
Current secondary battery electrodes face challenges in achieving high density, excellent adhesiveness to current collectors, flexibility, and viscosity retention, particularly when using nickel-rich active materials, which can lead to gelling and electrode unevenness.
Innovation Solution
A binder composed of a fluorine-containing polymer with specific molecular weight and composition, including polymerized units based on vinylidene fluoride, tetrafluoroethylene, and a monomer represented by formula (2-2), combined with polyvinylidene fluoride, is used to enhance electrode density, adhesiveness, flexibility, and viscosity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel-rich active materials are used to increase energy density, then battery capacity is improved, but gelling and electrode unevenness occur
Solution Approach 1:
The patent modifies the binder's molecular weight parameters (number average molecular weight Mn: 100,000-500,000, weight average molecular weight Mw: 300,000-1,500,000, and Mw/Mn ratio: 1.05-2.0) to optimize the electrode slurry properties. This parameter optimization prevents gelling and maintains electrode uniformity while using nickel-rich active materials for high capacity
Solution Approach 2:
The patent uses a fluorine-containing polymer as a composite binder material that combines multiple functional properties: adhesion to current collector, flexibility, and gelling resistance. This composite material approach allows the electrode to maintain stability and uniformity even with nickel-rich active materials
2Quantity of substance
If electrode thickness is increased to improve energy density, then battery capacity is improved, but flexibility and adhesion are reduced
Solution Approach 1:
The patent optimizes the binder's molecular weight parameters (Mn: 100,000-500,000, Mw: 300,000-1,500,000, Mw/Mn: 1.05-2.0) to achieve the right balance between electrode density and flexibility. This allows thick electrodes to maintain good adhesion to the current collector while achieving high energy density
3Quantity of substance
If binder amount is reduced to improve electrode density, then electrode density is improved, but adhesion and flexibility are reduced
Solution Approach 1:
The patent optimizes the binder's molecular weight parameters to maximize the efficiency of the binder material. This allows achieving high electrode density with minimal binder content while maintaining adequate adhesion and flexibility through optimized molecular characteristics
Solution Approach 2:
The fluorine-containing polymer's unique molecular structure and composition provide multiple functions in a single material, allowing reduced binder quantity while maintaining adhesion, flexibility, and gelling resistance simultaneously
Data Source
AI summary
A binder for a secondary battery containing a fluorine-containing polymer (A) and polyvinylidene fluoride (B). The fluorine-containing polymer (A) contains a polymerized unit based on vinylidene fluoride, a polymerized unit based on tetrafluoroethylene, and a polymerized unit based on a monomer (2-2) represented by the following formula (2-2):wherein R5, R6, and R7 are each independently a hydrogen atom or a C1-C8 hydrocarbon group; R8 is a C1-C8 hydrocarbon group; and Y1 is an inorganic cation or an organic cation. Also disclosed is an electrode mixture and an electrode for a secondary battery including the binder, and a secondary battery including the electrode.