Porous Electrode Assembly Coating for Swelling-Resistant Li-Ion Cells
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Solution Overview
Problem
Existing lithium secondary batteries face safety issues due to the generation of oxygen during charging, leading to potential ignition and short circuits, and the formation of a porous coating layer on the electrode is challenging, causing swelling and porosity problems.
Innovation Solution
A method involving multiple rolling steps to form a porous coating layer on the positive electrode active material layer, using polymer or ceramic particles with a specific zeta potential, to achieve a porosity of 35% to 45% initially and 20% to 30% finally, along with a thin mixed layer thickness, ensuring electrical insulation and ion movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous coating layer is formed on the positive electrode to replace or assist the separator, then the safety of the lithium secondary battery is improved, but the electrode active material layer becomes swollen and damaged during the coating formation process
Solution Approach 1:
The patent applies a preliminary rolling step before forming the coating layer to compress the positive electrode active material layer and prevent swelling. This preliminary action prepares the electrode structure to withstand the subsequent coating formation process without damage, thereby maintaining electrode integrity while still achieving the safety benefits of the porous coating layer
Solution Approach 2:
The patent uses a polymer binder with specific viscosity characteristics to cushion the mechanical stress during coating layer formation. The binder absorbs the expansion pressure, preventing damage to the active material layer while allowing the porous coating to form effectively, thus protecting electrode integrity during the safety-enhancing coating process
2Reliability
If a porous coating layer is formed on the positive electrode, then the safety is improved, but it becomes difficult to achieve appropriate porosity of the positive electrode active material layer
Solution Approach 1:
The patent controls the porosity of the positive electrode active material layer by adjusting the rolling pressure and duration parameters. By optimizing these physical parameters, the patent achieves the appropriate porosity range (30-50%) needed for both safety performance and manufacturing quality, resolving the contradiction between safety improvement and manufacturing precision
Solution Approach 2:
The patent employs a porous coating layer with specific pore structure and porosity characteristics that allows ion transport while maintaining safety. The porous structure is designed to work synergistically with the controlled porosity of the underlying active material layer, achieving both safety enhancement and manufacturing precision through coordinated porous material design
3Ease of manufacture
If the medium of the coating layer composition is impregnated with the positive electrode, then the coating layer can be formed, but the electrode active material layer is swollen
Solution Approach 1:
The patent modifies the viscosity parameter of the polymer binder used in the coating layer composition. By adjusting the viscosity to an optimal range, the patent enables effective impregnation and coating formation while minimizing the swelling effect on the active material layer, thus maintaining ease of manufacture without compromising electrode integrity
Solution Approach 2:
The patent creates a gradient in the coating layer composition, with higher polymer concentration near the electrode surface and lower concentration deeper in the coating. This local quality variation allows the coating to form effectively at the interface while reducing the overall impregnation depth, thereby preventing excessive swelling and maintaining electrode strength
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 enhances the safety and capacity of lithium secondary batteries by preventing short circuits and ignition, while maintaining appropriate porosity and mechanical integrity of the electrode layers.
Implementation Method 1
The porous coating layer can electrically insulate the positive electrode and the negative electrode from each other while enabling ion movement between the positive electrode and the negative electrode
Implementation Method 2
the first rolling step is performed such that a porosity of the positive electrode active material layer is 35% to 45%, and the second rolling step is performed such that a porosity of the positive electrode active material layer is 20% to 30%
Data Source
AI summary
A method of manufacturing an electrode assembly is provided. The method comprises: (S1) applying a positive electrode slurry onto a positive electrode current collector and drying the same to form a positive electrode active material layer, (S2) rolling the positive electrode current collector and the positive electrode active material layer, (S3) applying a coating layer slurry onto the positive electrode active material layer and drying it to form a positive electrode stack including the coating layer, (S4) rolling the positive electrode stack, and (S5) stacking a negative electrode on the coating layer to manufacture an electrode assembly.