Cylindrical Jelly Roll Tape Positioning for Battery Core Cracking
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Solution Overview
Problem
Lithium secondary batteries with nickel-rich positive electrode materials experience cracking at the core portion during the winding process due to stress concentration caused by the overlap of the tape with the stepped portion of the winding core member, leading to degradation and reduced durability.
Innovation Solution
A cylindrical jelly roll design where the tape on the positive electrode is positioned around the circumference of the winding core member to avoid the area where the first and second winding cores are spaced apart, using a nickel-rich positive electrode active material and a polypropylene tape to prevent stress concentration and cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the tape is positioned at the stepped portion of the winding core member to secure the positive electrode structure, then the structural stability is improved, but stress concentration occurs leading to cracking at the core portion
Solution Approach 1:
The patent extracts the harmful overlap between the tape and the stepped portion of the winding core member. By repositioning the tape to a location that does not coincide with the stepped portion, the source of stress concentration is eliminated, preventing cracking while maintaining structural stability through proper tape placement.
2Quantity of substance
If nickel-rich positive electrode active material is used to increase energy density, then the energy density is improved, but the brittleness increases making the electrode more susceptible to cracking
Solution Approach 1:
The patent applies preliminary action by carefully positioning the tape on the positive electrode before the winding process, ensuring that the tape does not overlap with the stepped portion of the winding core member. This preventive measure is taken in advance to avoid stress concentration and cracking, allowing the use of brittle nickel-rich materials without compromising electrode integrity.
Data Source
AI summary
A lithium secondary battery is provided which includes a cylindrical jelly roll in which an electrode assembly having a stacked structure including a positive electrode is wound cylindrically, wherein a semi-cylindrical first winding core and second winding core are spaced apart from each other by a predetermined interval, the positive electrode includes a non-coated portion sheet having a positive electrode tab fused thereto and a coated portion sheet, and the non-coated portion sheet and the coated portion sheet are attached by a tape to provide the positive electrode, one end of the positive electrode is positioned at the core portion of the cylindrical jelly roll, and a portion of the positive electrode having the tape is positioned around a circumference of the winding core member such that it avoids a portion where the first winding core is spaced apart from the second winding core by the predetermined interval.