Graded Binder Distribution in Battery Electrode Active Material Layer
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries have insufficient cycle characteristics due to excessive or insufficient binder usage, which affects discharge capacity and peeling strength of the electrode active material layer.
Innovation Solution
The electrode active material layer in the battery is configured with a binder distribution that increases continuously from the outer surface toward the core, with a reduced binder amount near the outer surface to prevent peeling and a higher amount near the core for improved adhesion, using a method that involves applying multiple electrode active material slurries with varying solvent content and drying speeds to achieve optimal binder distribution.
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 core and lower concentration toward the outer surface. This local variation in binder quality provides sufficient peeling strength at the interface while minimizing binder interference with charge-discharge reactions in the active material regions.
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 present near the core to ensure strong adhesion and prevent peeling, while the binder amount decreases toward the outer surface to minimize its negative impact on discharge capacity. This resolves the contradiction by providing just enough binder where needed without excessive binder throughout.
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 invention employs a graded binder distribution where concentration varies continuously from the core to the outer surface. This non-uniform distribution improves cycle characteristics by optimizing both adhesion and electrochemical performance, while the gradient can be achieved through controlled slurry application and drying processes.
Solution Approach 2:
The binder distribution is controlled in the thickness dimension of the electrode layer, creating a gradient structure. This dimensional approach allows optimization of properties through the layer depth, achieving better cycle characteristics without fundamentally changing the manufacturing process complexity.
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
This configuration enhances the cycle characteristics of the battery by maintaining higher capacity retention, reducing internal resistance, and improving safety against impact, as demonstrated by increased capacity retention and lower maximum temperatures in impact tests.
Implementation Method 1
The binder is distributed in the electrode active material layer such that the amount of the binder increases continuously from an outer surface of the electrode active material layer toward the core
Implementation Method 2
Nonaqueous electrolyte secondary batteries are widely used as power supplies for driving portable devices such as cellular phones, smart phones, and notebook PCs because of their high energy density and high capacity
Data Source
AI summary
An electrode active material layer containing an electrode active material and a binder. The binder is distributed in the electrode active material layer such that the amount of the binder increases continuously from an outer surface of the electrode active material layer toward the core. The amount of the binder present in the electrode active material layer per unit thickness is less than 10 in a region extending from a position 90% of the thickness of the electrode active material layer to a position 100% of the thickness of the electrode active material layer from a surface of the electrode active material layer facing the core, 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 in the electrode active material layer.