Secondary Battery Anode Binder Distribution Against Peeling
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Solution Overview
Problem
In non-aqueous electrolyte secondary batteries, the distribution of rubber-based and water-soluble polymer-based binders affects the binding force between the anode active material and the current collector, leading to issues such as peeling of the anode mixture layer and reduced battery performance.
Innovation Solution
The anode mixture layer is optimized with a specific distribution of rubber-based binder (1.0 wt % to 2.5 wt %) and water-soluble polymer-based binder (0.5 wt % to 1.5 wt %), where the rubber-based binder content is higher near the anode current collector and the water-soluble polymer-based binder is more prominent on the surface, with a CA/CB ratio greater than 1.0 at intervals 0 to 3 and less than 1.0 at intervals 7 to 10, to enhance adhesion and prevent peeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the same amount of rubber-based binder and water-soluble polymer-based binder is used throughout the anode mixture layer, then the manufacturing process is simple, but the adhesion between the anode active material and current collector is insufficient, causing peeling
Solution Approach 1:
The patent applies local quality by creating different binder compositions at different positions within the anode mixture layer. Specifically, the rubber-based binder is concentrated near the current collector (first region) to provide strong adhesion, while the water-soluble polymer-based binder is concentrated toward the active material surface (second region) to provide flexibility and prevent peeling. This spatial variation in binder composition resolves the contradiction between simple manufacturing and strong adhesion.
2Strength
If rubber-based binder content is increased to improve adhesion, then binding force between anode active material and current collector is enhanced, but the anode mixture layer becomes too rigid and lithium ion diffusion is hindered
Solution Approach 1:
The patent resolves this contradiction by locally concentrating the rubber-based binder in the first region near the current collector where adhesion is needed, while limiting its presence in the second region near the active material surface. The water-soluble polymer-based binder is then concentrated in the second region to provide flexibility and maintain lithium ion diffusion pathways. This spatial separation of binder functions eliminates the harmful effect of excessive rubber binder on lithium ion diffusion while maintaining strong adhesion.
3Reliability
If water-soluble polymer-based binder content is increased to improve flexibility and prevent peeling, then peeling resistance is enhanced, but adhesion to current collector is reduced
Solution Approach 1:
The patent resolves this contradiction by creating a spatially differentiated binder distribution where the water-soluble polymer-based binder is concentrated in the second region toward the active material surface, providing flexibility and peeling resistance where needed. Meanwhile, the rubber-based binder is concentrated in the first region near the current collector to provide strong adhesion. This local specialization of binder functions eliminates the trade-off between peeling resistance and adhesion strength.
Data Source
AI summary
An anode for a non-aqueous electrolyte secondary battery includes: an anode current collector; and an anode mixture layer formed on the anode current collector, containing an anode active material, a conductor, a rubber-based binder, and a water-soluble polymer-based binder. The anode mixture layer comprises, relative to a total weight thereof, 1.0-2.5 wt % of the rubber-based binder and 0.5-1.5 wt % of the water-soluble polymer based binder. When the anode mixture layer is divided into ten equal parts in the thickness direction based on the current collector, a ratio (CA/CB) at an interval of 0 to 3 of a content ratio (CA) of the rubber-based binder to a total content of the rubber-based binder to a content ratio (CB) of the water-soluble polymer-based binder to a total content of the water-soluble polymer-based binder is larger than 1.0, and a ratio (CA/CB) at an interval of 7 to 10 is smaller than 1.0.