Dry Positive Electrode Lamination for Density and Adhesion Control
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Solution Overview
Problem
Conventional methods for manufacturing lithium secondary battery positive electrodes face limitations in achieving suitable density and porosity of the positive electrode mixture layer and effective adhesion between the mixture layer and the current collector, often resulting in defects like pinholes, cracks, and reduced adhesion due to uneven solvent evaporation and inappropriate rolling pressures.
Innovation Solution
A dry method involving lamination of a mixture film containing a positive electrode active material, conductive material, and binder on a current collector, with controlled compression ratios and temperatures to achieve a density of 2 to 4 g/cm³ and effective adhesion, using a press roll to integrate the mixture film with the current collector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a positive electrode slurry is prepared using a solvent and coated on a current collector, then the positive electrode can be manufactured with continuous coating process, but the solvent evaporation causes defects such as pinholes or cracks and uneven drying creates powder floating phenomenon
Solution Approach 1:
The patent removes the solvent from the electrode manufacturing process entirely, using a dry mixture of positive electrode active material, conductive material, and binder instead of a slurry. This extraction of the harmful solvent eliminates the pinholes and cracks that form during evaporation, while maintaining continuous manufacturing capability through dry coating methods
Solution Approach 2:
The patent changes the physical state parameter of the electrode mixture from liquid slurry to dry powder form. By transforming the mixture into a dry state with controlled particle size distribution and using it in a dry coating process, the patent eliminates solvent-related defects while achieving uniform powder distribution without floating phenomena
2Manufacturing precision
If the gap between press rolls is reduced to increase density of the positive electrode mixture layer, then the density increases, but the porosity becomes lower than target or the active material or current collector is damaged
Solution Approach 1:
The patent optimizes the compression ratio parameter within a specific range (10-30%) to achieve the desired density without excessive pressure. By controlling the compression ratio as a key parameter rather than simply reducing the gap, the patent achieves target density while preventing damage to the active material and current collector
Solution Approach 2:
The patent employs dynamic control of the pressing process, adjusting the compression ratio based on the specific requirements of the electrode mixture. The pressing force is optimized to be sufficient for adhesion and density but not excessive to cause damage, creating a balanced dynamic pressing condition
3Object-affected harmful factors
If the gap between press rolls is increased to prevent damage, then the damage is avoided, but the adhesion between the positive electrode mixture layer and current collector is lowered
Solution Approach 1:
The patent optimizes the compression ratio parameter within a specific range (10-30%) to achieve the desired density without excessive pressure. By controlling the compression ratio as a key parameter rather than simply reducing the gap, the patent achieves target density while preventing damage to the active material and current collector
Solution Approach 2:
The patent uses a primer layer as an intermediary between the current collector and the positive electrode mixture layer. This primer layer enhances adhesion without requiring excessive pressing force, allowing the use of optimized compression ratios that prevent damage while ensuring strong bonding through the intermediary layer
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
The method ensures a positive electrode with appropriate density and porosity, enhancing adhesion between the mixture layer and the current collector, thereby improving the quality and performance of the lithium secondary battery.
Implementation Method 1
laminating a mixture film including a positive electrode active material, a conductive material and a binder on one or both surfaces of a current collector, wherein, during the lamination, the mixture film satisfies a compression ratio
Data Source
AI summary
The present technology relates to a dry method of manufacturing a positive electrode for a lithium secondary battery, a positive electrode manufactured thereby, and a lithium secondary battery including the same. Thereby, a positive electrode including a positive electrode mixture layer with an appropriate density, and effective adhesion between the positive electrode mixture layer and the current collector may be realized.