Electrode Binder Gradient for Rapid Charging
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Solution Overview
Problem
High electrode density in large cells for high-energy EVs limits Li ion diffusion into the anode, leading to cell deterioration, and existing methods to improve binder distribution are limited by detachment issues during charging and discharging.
Innovation Solution
A dual-layer electrode structure with a binder content gradient, where the A region has a higher binder content than the B region, applied in a specific pattern to enhance interfacial adhesion and facilitate Li-ion penetration, using a styrene butadiene rubber (SBR)-based binder to maintain adhesion while reducing surface binder content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If binder content is lowered to improve rapid charging performance, then Li ion diffusion is improved, but electrode mixture layer detachment occurs during notching or charging/discharging process
Solution Approach 1:
The patent applies local quality by creating a binder content gradient within the electrode active material layer. The binder content is higher at the interface with the current collector (A region) to ensure strong adhesion and prevent detachment, while the binder content is lower in the bulk and surface regions (B region) to facilitate Li ion diffusion and improve rapid charging performance. This spatial variation in binder concentration resolves the contradiction between adhesion and ion diffusion.
Solution Approach 2:
The patent changes the binder content parameter continuously across the electrode thickness direction, creating a gradient distribution rather than a uniform composition. By controlling the binder content to range from higher at the current collector interface to lower at the surface, the patent optimizes both adhesion strength and Li ion transport properties simultaneously, resolving the technical contradiction.
2Reliability
If high binder content is formed at current collector interface to suppress detachment, then interfacial adhesion is improved, but binder particles move to surface during drying process preventing ideal distribution
Solution Approach 1:
The patent applies preliminary action by pre-distributing the binder in a controlled gradient pattern within the electrode active material layer before the drying process occurs. The binder is intentionally positioned with higher concentration at the current collector interface and lower concentration toward the surface in the slurry state. This preliminary spatial arrangement ensures that even though some binder migration occurs during drying, the final distribution still maintains the desired gradient structure with adequate interfacial adhesion.
3Quantity of substance
If electrode density is increased for high-energy EVs, then energy density is improved, but Li ion diffusion into anode is limited causing cell deterioration
Solution Approach 1:
The patent applies local quality by creating regions with different binder concentrations within the electrode active material layer. The B region with lower binder content provides channels for efficient Li ion diffusion, while the A region with higher binder content at the interface ensures structural integrity. This local differentiation allows the electrode to maintain high overall density for energy storage while providing localized pathways for rapid ion transport.
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 content gradient improves interfacial adhesion, reduces electrode detachment, and enhances rapid charging performance by facilitating Li-ion penetration and ion conductivity, while maintaining overall binder content similar to existing technologies.
Implementation Method 1
when the cells are charged with a high current density, there is a limit to a diffusion of Li ions into an anode
Implementation Method 2
improving an interfacial adhesion between a current collector and an electrode active material layer by efficiently distributing a binder inside an electrode
Data Source
Figure 1A~1B
Figure 2A~2B
AI summary
Provided is an electrode for a secondary battery including: a current collector; and an electrode active material layer located on at least one surface of the current collector, and including an electrode active material and a binder, in which the electrode active material layer includes A region and B region crossing in a direction from one side to the other side of the electrode active material layer in a width direction, the A region has a higher binder content than that of the B region, and the A region and B region have a continuous binder content gradient at a boundary of each region.