Prismatic Battery Electrode Winding for Thickness Uniformity
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Solution Overview
Problem
The configuration of prismatic batteries results in variations in thickness due to differences in the total area of electrodes at opposite ends, leading to reduced capacity utilization and inefficient use of the battery case volume.
Innovation Solution
The electrode assembly is formed by winding a positive electrode, a negative electrode, and a separator in longitudinal directions, with a flat portion and folded portions, where the negative electrode active material layer is initially formed on one surface and later on both surfaces, and the winding start positions are optimized to minimize stress and ensure even curvature, allowing for uniform thickness and increased capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the electrode assembly is formed by spirally winding positive and negative electrodes with different end portion positions, then the battery can be constructed with practical winding configuration, but variations in thickness occur at opposite ends of the electrode assembly
Solution Approach 1:
The patent applies preliminary action by forming the negative electrode active material layer on both surfaces of the negative electrode core member in advance, before the winding process. Specifically, the active material layer is formed on both surfaces up to a predetermined position that extends beyond the winding start position. This preliminary formation ensures that when the electrodes are wound, both surfaces of the negative electrode have active material available, compensating for the thickness variations that occur during winding and achieving uniform overall thickness in the electrode assembly.
2Ease of manufacture
If the negative electrode active material layer is formed only on one surface to simplify manufacturing, then the manufacturing process is easier, but the total area of active material is reduced
Solution Approach 1:
The patent applies local quality by differentiating the active material layer formation based on location. The active material layer is formed on both surfaces of the negative electrode core member up to a predetermined position that extends beyond the winding start position. In the region beyond this predetermined position, the active material layer may be formed on only one surface or not at all. This localized differentiation ensures that sufficient active material is available in the critical winding region while simplifying manufacturing in non-critical regions.
3Quantity of substance
If the electrode assembly is designed to maximize capacity, then the total area of active material is increased, but the battery case volume utilization becomes inefficient due to thickness variations
Solution Approach 1:
The patent applies parameter changes by modifying the extent of the negative electrode active material layer formation. The predetermined position up to which the active material layer is formed on both surfaces is set to extend beyond the winding start position by a specific distance. This parameter adjustment ensures that the electrode assembly achieves uniform thickness throughout, maximizing the usable volume of the battery case while maintaining high capacity through sufficient active material area.
Data Source
AI summary
A prismatic battery includes an electrode assembly including: a positive electrode including a belt-shaped positive electrode core member and a positive electrode active material layer formed on both surfaces thereof; a negative electrode including a belt-shaped negative electrode core member and a negative electrode active material layer formed on both surfaces thereof; and a belt-shaped separator. The electrode assembly is formed by winding the positive electrode, the negative electrode, and the separator in the longitudinal directions thereof. The negative electrode has, in an end portion thereof from which winding is started, a one-sided active material layer portion in which the negative electrode active material layer is provided only on one surface of the negative core member. The one-sided active material layer portion terminates at a predetermined position between positions at which the negative electrode is folded for the second time and for the third time.