Wet Electrode Stacking with In-Process Pressing
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Solution Overview
Problem
The manufacturing of secondary batteries for electric vehicles and hybrid electric vehicles faces issues with cracking of electrode active material slurry during drying, leading to reduced battery performance, and the formation of irregularities during unit cell stacking, which increases internal and contact resistance.
Innovation Solution
A battery manufacturing method where unit cells are stacked with a positive electrode active material layer and a negative electrode active material layer containing an electrolytic solution, with each unit cell being pressed during stacking to adjust thickness and flatten irregularities, reducing internal and contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If electrode active material slurry is dried to form dry electrodes, then the electrodes become structurally stable, but cracking occurs during drying which reduces battery performance
Solution Approach 1:
The patent changes the physical state parameter of the electrode from dry to wet by maintaining the electrode active material slurry in a non-dried state containing electrolytic solution. This parameter change eliminates the cracking issue that occurs during drying while maintaining electrode functionality through the liquid electrolyte medium.
2Productivity
If unit cells are molded by pressing all at once after stacking, then the process is efficient, but irregularities remain in the surface and interior of unit cells which increases internal resistance
Solution Approach 1:
The patent divides the molding process into segmented steps where pressing is performed at different stages of unit cell stacking rather than all at once. This segmentation allows progressive compression that eliminates irregularities in the surface and interior of unit cells, reducing internal resistance while maintaining manufacturing efficiency.
Solution Approach 2:
The patent applies preliminary pressing actions during the stacking process itself, before final assembly is complete. By pressing unit cells progressively as they are stacked, the method prevents irregularity formation and ensures uniform density throughout the battery structure, reducing internal resistance before the final product is completed.
3Reliability
If electrodes containing electrolytic solution are used, then cracking is prevented, but the electrodes are wet and more susceptible to formation of creases in current collector and separator
Solution Approach 1:
The patent applies preliminary pressing actions during the stacking process to flatten and stabilize the wet electrodes, current collectors, and separators before final assembly. This preliminary action prevents crease formation by eliminating irregularities while the electrodes are still accessible and deformable, maintaining both electrode integrity and structural flatness.
Data Source
AI summary
A method for manufacturing a battery has a stacking step in which a plurality of unit cells are stacked, the unit cells being such that a positive electrode obtained by a positive electrode active material layer containing an electrolytic solution disposed on a positive electrode current collector, and a negative electrode obtained by a negative electrode active material layer containing an electrolytic solution disposed on a negative electrode current collector with a separator interposed therebetween. In the stacking step, each time one of the unit cells is stacked, the stack of the unit cells are pressed from the stacking direction.