Cylindrical Battery Electrode Lead Layout for Circularity and Warpage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Cylindrical non-aqueous electrolyte secondary batteries face challenges in achieving high capacity and output while maintaining electrode circularity and long-term reliability, due to issues such as warpage of the positive electrode and dropping of active material at the boundary between double-sided and single-sided applied portions.
Innovation Solution
The battery design includes an electrode assembly with a long strip-shaped positive and negative electrode, both having current collectors with mixture layers on both surfaces. The positive electrode lead has a protrusion and is fixed to the current collector, while the negative electrode lead is also fixed with a protrusion. The design features multiple double-sided current collector exposed portions for the positive electrode and a double-sided negative electrode current collector exposed portion, which enhances the circularity and reduces warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a single-sided positive electrode mixture unapplied portion is formed at the position between 1/3 and 2/3 of the radius of the electrode assembly, then the circularity of the electrode assembly is improved and resistance is reduced, but warpage occurs on the positive electrode in the longitudinal direction and active material dropping occurs at the boundary between single-sided and double-sided applied portions
Solution Approach 1:
The positive electrode mixture unapplied portion is divided into two separate regions: a first unapplied portion on the first surface and a second unapplied portion on the second surface. Both surfaces have unapplied portions at substantially the same position between 1/3 and 2/3 of the radius, creating a double-sided unapplied portion configuration. This segmentation prevents warpage by distributing the stress evenly across both surfaces while maintaining the circularity benefits.
Solution Approach 2:
The invention transitions from a single-sided unapplied portion configuration to a double-sided unapplied portion configuration, where the unapplied portions are positioned asymmetrically on each surface but at corresponding locations. This creates a balanced asymmetric structure that prevents warpage while maintaining the circularity improvement.
2Loss of energy
If the positive electrode has a single-sided mixture unapplied portion, then the current collecting path is shortened and resistance is reduced, but the positive electrode mixture layer is hardly compressed in rolling and active material dropping occurs
Solution Approach 1:
The unapplied portion is segmented to appear on both the first and second surfaces of the positive electrode current collector at corresponding positions. This double-sided segmentation allows the mixture layers on both surfaces to be properly compressed during rolling while maintaining shortened current collecting paths, thereby reducing resistance without causing active material dropping.
Solution Approach 2:
The unapplied portion configuration is extended from a single-sided (2D) approach to a double-sided (3D) approach, where unapplied portions exist on both surfaces of the current collector. This dimensional change allows uniform compression of mixture layers during rolling while maintaining the electrical benefits of shortened current paths.
3Loss of energy
If leads are installed at both end portions of the negative electrode in the longitudinal direction, then low resistance is realized, but the circularity of the electrode assembly deteriorates due to distorted shape
Solution Approach 1:
Instead of installing leads at the end portions of the negative electrode as in conventional designs, the invention inverts the approach by positioning the positive electrode lead and negative electrode lead at corresponding positions between 1/3 and 2/3 of the radius. This inverted lead arrangement shortens current collecting paths while maintaining electrode assembly circularity.
Solution Approach 2:
The lead positioning strategy transitions from a longitudinal end-positioning approach to a radial position-based approach, where leads are positioned at specific radial distances (1/3 to 2/3 of radius) from the center. This dimensional change in lead placement optimizes both electrical performance and mechanical shape.
Data Source
AI summary
In the present invention, in a positive electrode, a positive electrode current collector-exposed portion, in which a positive electrode current collector is exposed, has two or more double-sided positive electrode current collector-exposed sections in which a positive electrode current collector is exposed in substantially identical regions on both surfaces in the longitudinal direction of the positive electrode. A negative electrode has at least one double-sided negative electrode current collector-exposed section in which a negative electrode current collector is exposed in substantially identical regions on both surfaces in the longitudinal direction of the negative electrode. The double-sided negative electrode current collector-exposed section faces the double-sided positive electrode current collector-exposed section via a separator. The two or more double-sided positive electrode current collector-exposed sections include a lead-fixing exposed portion to which a positive electrode lead is fixed. A negative electrode lead is fixed to the double-sided negative electrode current collector-exposed section. In the positive electrode, at least a part of the positive electrode lead is disposed at a point of overlap, in the height direction, with a negative electrode lead-facing position which faces the negative electrode lead via the separator.