Wound Electrode Assembly Structure for Curved-Edge Crack Prevention
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Solution Overview
Problem
The repetitive contraction and expansion of secondary battery jelly rolls during charging and discharging lead to mechanical stress, causing cracks and degradation in battery performance due to uneven tension in the outer electrode substrate, particularly in wound electrode assemblies like pouch-type batteries.
Innovation Solution
An electrode assembly design featuring a protection member positioned at the curved portion of the first electrode, with a thickness increasing towards the outer portion, and an insulating member to prevent cracks, using materials like polypropylene, polyimide, or polyethylene propylene tape, ensuring the protection member does not overlap the electrode tab.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a wound electrode assembly structure is used to achieve compact battery design, then productivity and space utilization are improved, but mechanical stress concentration occurs at curved portions leading to cracks and reduced reliability
Solution Approach 1:
A protection member is attached in advance to the curved portion of the electrode substrate before winding, serving as a cushioning layer that absorbs and distributes mechanical stress during battery operation. This prevents stress concentration that would otherwise cause cracks at the vulnerable curved portions of the wound electrode assembly.
Solution Approach 2:
The protection member is selectively applied only to the curved portion of the electrode substrate where stress concentration occurs, rather than covering the entire substrate. This localized approach provides targeted stress relief at the critical area while maintaining the overall structural integrity and electrical performance of the electrode assembly.
2Weight of moving object
If the electrode substrate is made thinner to reduce battery weight and size, then weight and volume are reduced, but mechanical strength decreases making the substrate more susceptible to cracks under stress
Solution Approach 1:
The electrode substrate is combined with a protection member to form a composite structure. The protection member, made from materials such as polypropylene, polyimide, or ethylene propylene copolymer, provides enhanced mechanical strength to the thin substrate while maintaining the lightweight characteristic. This composite approach allows the substrate to be sufficiently thin for weight reduction while the protection member prevents crack formation under stress.
3Reliability
If a protection member is added to prevent cracks at curved portions, then reliability is improved, but device complexity and manufacturing steps increase
Solution Approach 1:
The protection member is implemented as a thin film or tape made from flexible polymer materials that can conform to the curved portion of the electrode substrate. This thin-film approach provides effective crack prevention without adding significant structural complexity or thickness to the electrode assembly, maintaining simplicity while improving reliability.
Data Source
AI summary
An electrode assembly includes a first electrode, an outer separator on the first electrode, a second electrode on the outer separator, and an inner separator on the second electrode, wherein a protection member is at an end of one side of the first electrode, and a position of the protection member is at a curved portion of the first electrode in a wound state.