Negative Electrode Reflectance Inspection for Binder Uniformity
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Solution Overview
Problem
Existing methods for manufacturing lithium ion secondary batteries fail to efficiently assess binder distribution on the electrode surface, leading to potential localization issues that can affect battery performance and productivity.
Innovation Solution
A method involving measuring the reflectance of the negative electrode plate's coating surface at specific angles to determine binder distribution, ensuring it falls within a range of 15 to 35% for optimal uniformity and preventing localization, thereby assessing the quality of the electrode without lowering productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional drying methods are used to evaporate solvent from electrode mixture, then drying efficiency is improved, but binder localization occurs on the electrode surface
Solution Approach 1:
The drying process is divided into multiple temperature zones (first drying zone at lower temperature, second drying zone at higher temperature) to segment the evaporation process. This segmentation allows gradual solvent removal that prevents binder localization while maintaining efficient drying throughput.
Solution Approach 2:
Different regions of the electrode undergo different drying conditions - the surface region experiences controlled lower temperature drying first, then higher temperature drying, while the bulk experiences progressive drying. This local quality approach ensures uniform binder distribution throughout the electrode structure.
2Ease of manufacture
If binder distribution is not properly controlled during drying, then manufacturing process is simplified, but electrode surface resistance increases and peeling occurs
Solution Approach 1:
The electrode mixture is pre-formulated with specific binder content and the coating is applied with controlled thickness before drying. This preliminary preparation ensures that during the subsequent multi-zone drying process, the binder remains uniformly distributed and prevents surface localization, thereby maintaining electrode reliability.
Solution Approach 2:
The drying process parameters (temperature zones, residence times) are optimized based on feedback from binder distribution characteristics. The multi-zone temperature control provides feedback mechanisms that adjust drying intensity to maintain uniform binder distribution, preventing surface resistance increase and peeling.
3Productivity
If rapid drying is performed to increase production speed, then productivity is improved, but binder localization on surface occurs
Solution Approach 1:
The drying process uses dynamic temperature control with multiple zones instead of static uniform heating. The first drying zone operates at lower temperature while the second zone operates at higher temperature, creating a dynamic gradient that moves through the electrode during processing. This dynamic approach maintains binder uniformity even at high production speeds.
Solution Approach 2:
The multi-zone drying system operates continuously without interruption, with each zone performing its drying function simultaneously as the electrode passes through. This continuous action maintains high productivity while the staged temperature approach prevents binder localization, achieving both speed and uniformity.
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 approach allows for quick and non-invasive assessment of binder distribution, ensuring uniformity and preventing issues like increased surface resistance and peeling, thus maintaining battery performance and productivity.
Implementation Method 1
measuring, after the coating and drying, a reflectance of a coating surface of the negative electrode plate... when an incident angle and a light receiving angle each fall within the range of 80° to 90°
Data Source
AI summary
A method of manufacturing a negative electrode plate for a non-aqueous secondary battery is disclosed, in which it is possible to assess whether or not a binder is localized in an electrode surface without lowering the productivity of the negative electrode plate. The method includes coating an electrode mixture containing at least a negative electrode active material and a binder to a current collector and drying the coated electrode mixture. The method includes an inspection step of measuring a reflectance of a coating surface of the negative electrode plate to thereby determine the quality of the negative electrode plate. If the reflectance of the coating surface of the negative electrode plate falls within a range of 15 to 35% when an incident angle and a light receiving angle each fall within the range of 80° to 90°, the negative electrode plate is determined to be excellent.