Gradient Binder Distribution in Electrode Active Material Layers
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face challenges in achieving good cycle characteristics due to the limitations of binder distribution in electrode active material layers, leading to insufficient lithium ion acceptance and electrolyte retention, which affects discharge capacity and peeling strength.
Innovation Solution
The electrode active material layer is configured with a gradient binder distribution, where the binder amount increases from the middle region towards the core and outer surface, ensuring balanced electrolyte retention and reduced peeling, with specific binder concentrations and drying processes optimizing the layer's structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an excessive amount of binder is used, then the peeling strength of the electrode active material layer is improved, but the discharge capacity decreases
Solution Approach 1:
The binder is distributed non-uniformly in the electrode active material layer, with higher concentration near the current collector and lower concentration toward the outer surface. This local quality variation ensures strong adhesion at the interface while maintaining high discharge capacity in the bulk, resolving the contradiction between peeling strength and discharge capacity.
2Quantity of substance
If an insufficient amount of binder is used, then the discharge capacity is improved, but the peeling strength of the electrode active material layer decreases
Solution Approach 1:
The binder concentration is optimized locally: sufficient binder is provided near the current collector to ensure strong adhesion and prevent peeling, while the outer regions contain less binder to maximize discharge capacity. This spatially varying composition resolves the contradiction between maintaining peeling strength and achieving high discharge capacity.
3Ease of manufacture
If the binder is uniformly distributed, then the manufacturing process is simplified, but the cycle characteristics are insufficient
Solution Approach 1:
The binder is distributed with a specific gradient (higher near current collector, lower toward outer surface) to optimize cycle characteristics. This non-uniform distribution improves reliability by ensuring proper adhesion and electrolyte retention, while the gradient can be achieved through controlled application processes.
Solution Approach 2:
The binder concentration parameter is varied spatially within the electrode layer, transitioning from high concentration near the current collector to low concentration at the outer surface. This parameter change optimizes both adhesion and cycle characteristics while maintaining manufacturing feasibility through controlled deposition.
Data Source
AI summary
An electrode active material layer containing an electrode active material and a binder. The electrode active material layer includes a portion containing the smallest amount of the binder in a middle region across the thickness of the electrode active material layer. The binder is distributed in the electrode active material layer such that the amount of the binder increases continuously from the portion toward the core and an outer surface of the electrode active material layer. Preferably, the amount of the binder present in the electrode active material layer per unit thickness is limited to more than 10 in a region extending 10% of the thickness from the outer surface of the electrode active material layer, with 10 being assigned to the amount of the binder present in the electrode active material layer per unit thickness if the binder is uniformly distributed.