Lithium Ion Electrode Binder Pattern Coating for Slipping Control
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Solution Overview
Problem
In the manufacturing of lithium ion secondary cell electrodes, the powder of granulated particles tends to slip on the current collector during leveling, leading to variations in basis weight and increased electric resistance, especially when molding speed is increased for improved productivity.
Innovation Solution
The method involves pattern-coating a binder liquid on the current collector to form a binder coat layer with alternating band-shaped coated and uncoated portions, and supplying granulated particles onto this layer, ensuring the widths of the coated and uncoated portions are within specific ratios relative to the average particle diameter, allowing for uniform leveling and pressing while minimizing electric resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the amount of binder is increased to improve adhesion between current collector and granulated particles, then the adhesion is improved, but the cell resistance increases
Solution Approach 1:
The binder is applied in a patterned manner with different coating amounts in different regions. Specifically, the binder coating amount is controlled to be 0.03-0.15 mg/cm² in the central region (within ±20% of width) and 0.01-0.05 mg/cm² in the side regions (beyond ±20% of width), creating local quality variations that optimize both adhesion and electrical properties
Solution Approach 2:
The binder coating is divided into different zones based on position across the current collector width. The central region receives a different binder amount compared to the side regions, segmenting the coating strategy to address different functional requirements in different areas
2Productivity
If the molding speed is increased to improve productivity, then the productivity is improved, but the basis weight uniformity deteriorates due to powder slipping
Solution Approach 1:
The binder is pre-coated on the current collector before granulated particles are supplied. This preliminary action creates an adhesive surface that prevents powder slipping during the subsequent high-speed molding process, ensuring basis weight uniformity even at increased productivity
Solution Approach 2:
The binder acts as an intermediary substance between the current collector and the granulated particles. By controlling the binder distribution pattern and amount, it mediates the interaction to prevent slipping while maintaining electrical conductivity
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 achieves high basis weight accuracy and low electric resistance, effectively preventing powder slipping and basis weight unevenness, even at higher molding speeds.
Implementation Method 1
improve the adhesion (binding ability) between the current collector and the granulated particles
Implementation Method 2
the deposited powder slides on the current collector
Data Source
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AI summary
The method for manufacturing an electrode for a lithium ion secondary cell proposed herein includes: a step of pattern-coating a binder liquid 21d on a current collector 12 and forming a binder coat layer 16, and a step of supplying granulated particles 32 onto the binder coat layer 16. The binder coat layer 16 is intermittently formed on the current collector 12 so that band-shaped coated portions 16a and band-shaped uncoated portions 16b are alternatingly adjacent to each other. The width t1 of the coated portions 16a, the width t2 of the uncoated portions 16b, and the average particle diameter R of the granulated particles 32 satisfy the following relationships: 0.53R ≤ t1 ≤ 10R; 0.66R ≤ t2 ≤ 10R; and 0.2 ≤ t1/t2 ≤ 3.75.