Zwitterionic Li-Battery Binder for Adhesion-Resistance Balance
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving high adhesive strength of active material layers to current collectors while minimizing electrical resistance, which affects their capacity and lifespan during rapid charging.
Innovation Solution
A binder for rechargeable lithium batteries is developed, comprising a combination of units derived from (meth)acrylic monomers with carboxylic acid groups, amide or nitrile groups, and Zwitterionic vinyl or (meth)acrylic monomers, which enhances adhesive strength and reduces electrical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional binders are used to ensure adhesive strength, then the active material layer adheres well to the current collector, but electrical resistance increases and capacity is reduced
Solution Approach 1:
The patent applies composite materials by combining carboxylic acid groups (for adhesion to current collector) with conductive polymer units (for electrical conductivity) and amide/nitrile groups (for additional adhesion and stability) within the same binder molecule. This creates a multi-functional composite binder that simultaneously provides strong adhesion and low electrical resistance, resolving the contradiction between adhesive strength and electrical resistance.
Solution Approach 2:
The binder structure implements local quality by positioning different functional groups in specific locations within the polymer chain: carboxylic acid groups are positioned to interact with the current collector surface, conductive polymer units are distributed to provide electrical pathways, and amide/nitrile groups are placed to enhance adhesion. This spatial arrangement of different functional properties within the binder enables simultaneous optimization of adhesion and conductivity.
2Speed
If rapid charging is implemented to improve charging speed, then charging time is reduced, but cell capacity is reduced through reduction in cell lifespan
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition and functional group distribution within the binder to create optimal conditions for rapid charging. The specific ratio of carboxylic acid groups to conductive polymer units is tuned to achieve the right balance between adhesion strength and electrical conductivity, enabling faster charge rates without excessive resistance that would generate heat and degrade the cell over time.
Solution Approach 2:
The multi-functional composite binder structure enables rapid charging by providing both strong adhesion to maintain electrode integrity during fast charge cycles and sufficient electrical conductivity to minimize resistive heating. The conductive polymer units create efficient electron transport pathways that reduce internal resistance, while the carboxylic acid and amide/nitrile groups ensure the active material remains firmly attached to the current collector, preventing degradation from mechanical stress during rapid charging.
Data Source
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AI summary
A binder for rechargeable lithium batteries and a rechargeable lithium battery including the binder are disclosed. The binder for rechargeable lithium batteries includes a unit derived from a (meth)acrylic monomer containing a carboxylic acid group or a carboxylic acid metal salt as a first monomer; a unit derived from a (meth)acrylic monomer containing an amide group or a nitrile group as a second monomer; and a unit derived from a Zwitterionic vinyl or (meth)acrylic monomer as a third monomer.