Tabless Secondary Battery Weld Layout for Low Internal Resistance
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Solution Overview
Problem
Lithium ion batteries with a tabless structure face reduced reaction area and degraded battery characteristics due to inadequate attention to the relationship between the winding termination end of the negative electrode plate and the coupled portion, leading to poor current collection efficiency.
Innovation Solution
A secondary battery design with a positive and negative electrode wound body structure, where the positive and negative electrode active material uncovered parts are welded to their respective collector plates at multiple points, and the welds are positioned relative to the winding termination ends to optimize current collection efficiency, reducing internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cutout is provided at a periphery of a negative electrode current collector to align with the winding termination end, then the internal resistance is reduced, but the reaction area of electrodes decreases and battery characteristics are degraded
Solution Approach 1:
The current collector plate is divided into multiple welding regions with multiple welds distributed across the plate surface. Instead of a single cutout alignment, multiple discrete welding points are created at different positions, segmenting the current collection function across multiple locations to reduce resistance without requiring a large continuous reaction area.
Solution Approach 2:
The solution transitions from one-dimensional alignment (cutout at periphery) to two-dimensional distribution (multiple welds across the plate surface). Welds are arranged in radial directions from the center, utilizing the radial dimension to optimize current collection without compromising the electrode reaction area.
2Reliability
If multiple welds are provided on the current collector plate, then the current collection efficiency is improved, but the device complexity increases
Solution Approach 1:
Different regions of the current collector plate have different welding characteristics. Welds are strategically positioned in radial directions from the center, with each weld serving a specific local function for current collection. This localized welding approach optimizes current collection efficiency without requiring uniform complexity across the entire structure.
Solution Approach 2:
The current collector plate serves multiple functions simultaneously: it collects current through multiple welds, provides structural support for the electrode wound body, and maintains electrical connectivity. The radial weld arrangement achieves both current collection and structural integrity in a single integrated component.
3Ease of manufacture
If the winding termination end is aligned with a cutout at the periphery, then the manufacturing is simplified, but the weld position relative to the winding termination end is not optimized
Solution Approach 1:
The winding termination end is pre-positioned at a specific location on the current collector plate before welding. The plate is designed with predetermined weld positions in radial directions, allowing the winding termination end to be aligned and welded at the optimal position before final assembly. This preliminary positioning ensures both manufacturing simplicity and optimal current collection efficiency.
Data Source
AI summary
A secondary battery improves current collection efficiency. A positive electrode current collector plate and a negative electrode current collector plate each include weld groups that are provided radially. A positive electrode active material uncovered part includes a first weld that is nearest to a winding termination end of a positive electrode foil, and a second weld that is second nearest to the winding termination end of the positive electrode foil after the first weld. A negative electrode active material uncovered part includes a third weld that is nearest to a winding termination end of a negative electrode foil, and a fourth weld that is second nearest to the winding termination end of the negative electrode foil after the third weld. The secondary battery satisfies Expressions (1) and (2) below:0≤LC1≤LC2 (1)0≤LA1≤LA2 (2)where LC1 represents a distance from the winding termination end of the positive electrode foil to the first weld in millimeters, LC2 represents a distance from the first weld to the second weld in millimeters, LA1 represents a distance from the winding termination end of the negative electrode foil to the third weld in millimeters, and LA2 represents a distance from the third weld to the fourth weld in millimeters.