Nonaqueous Electrolyte Battery Binder Distribution
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face challenges in achieving superior low-temperature output characteristics and high-temperature cycle characteristics due to issues with binder distribution and adhesion in the active material layer.
Innovation Solution
The active material layer is optimized with a specific binder distribution, where 8.5-9.5% binder is in the 0-10% thickness region and 9.5-11.5% in the 90-100% thickness region, with the binder-richest portion at 55-100% thickness, ensuring strong adhesion to the core plate and preventing fouling of compression devices, while maintaining effective ion intercalation and deintercalation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the binder content is increased to ensure strong bonding between the active material layer and core plate, then adhesion strength is improved, but the low-temperature output characteristics deteriorate due to excessive binder interfering with lithium ion intercalation and deintercalation
Solution Approach 1:
The binder content is made non-uniform across the thickness of the active material layer. Specifically, the binder content in the surface region (0-10% thickness) is controlled to be 8.5-9.5 mass% of total binder, while the binder-richest portion is located at 55-100% thickness. This local variation ensures strong adhesion at the core plate interface while maintaining sufficient lithium ion transport pathways in the bulk region, thereby resolving the contradiction between adhesion strength and low-temperature output characteristics.
2Reliability
If the binder content is increased to prevent active material layer separation, then bonding reliability is improved, but the high-temperature cycle characteristics deteriorate due to binder fouling compression devices
Solution Approach 1:
The binder distribution is optimized locally across the thickness direction. The binder content in the 90-100% thickness region is controlled to be 9.5-11.5 mass% of total binder, preventing excessive binder from migrating to the compression device surface during compression. Meanwhile, the binder-richest portion at 55-100% thickness ensures adequate bonding reliability. This local optimization prevents binder fouling while maintaining bonding reliability.
3Reliability
If the binder distribution is made non-uniform to improve adhesion and prevent fouling, then manufacturing complexity increases due to precise control requirements
Solution Approach 1:
The invention specifies precise parameter ranges for binder content distribution: 8.5-9.5 mass% in the 0-10% thickness region, 9.5-11.5 mass% in the 90-100% thickness region, with the binder-richest portion at 55-100% thickness. By defining these quantitative parameters, the complex non-uniform distribution control is transformed into measurable and controllable specification parameters, making the manufacturing process manageable while achieving improved reliability.
Data Source
AI summary
A nonaqueous electrolyte secondary battery includes a first electrode plate including a core plate and an active material layer including an active material and a binder, and disposed on a surface of the core plate; a second electrode plate; and a nonaqueous electrolyte. When the surface of the active material layer in contact with the core plate is taken as zero point, the amount of the binder in a 0%-10% thickness region X is 8.5 to 9.5 mass % of the total amount of the binder in the active material layer, the amount of the binder in a 90%-100% thickness region Y is 9.5 to 11.5 mass % of the total amount of the binder in the active material layer, and a binder-richest portion across the thickness of the active material layer resides in a 55%-100% thickness region across the thickness of the active material layer.