Pouch Cell Cap Structure for Gas Venting and Capacity Gain
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Solution Overview
Problem
Conventional pouch cells face limitations in shape and capacity due to material properties, leading to cracks and inefficiencies in gas management during charging and discharging.
Innovation Solution
A secondary battery design featuring a sheet-type outer packaging with a cap that exceeds the height of the electrode assembly, allowing for a larger internal space and minimizing shape changes, coupled with a pad to reduce heat transfer and pressure between batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pouch cell structure is used, then the battery can be manufactured with sealed pouch, but the pouch film develops cracks during forming process and gas management becomes inefficient
Solution Approach 1:
The pouch structure is segmented into multiple functional regions: a sealed pouch portion for containing electrodes and electrolyte, and an unsealed extension portion that communicates with the external environment through openings. This segmentation allows the sealed portion to maintain structural integrity while the unsealed portion enables efficient gas venting and prevents crack formation by accommodating volume changes.
Solution Approach 2:
The unsealed extension portion acts as an intermediary between the sealed pouch interior and the external environment. It provides a controlled interface for gas exchange and pressure equalization, preventing direct stress concentration on the sealed pouch film that would lead to cracks, while still allowing necessary gas management.
2Quantity of substance
If the pouch film forming depth is limited by material properties, then the pouch can be manufactured, but the battery capacity cannot be increased
Solution Approach 1:
The design extends the pouch structure in the vertical dimension by adding an unsealed extension portion that protrudes from the sealed pouch. This dimensional extension allows increased electrode assembly capacity without requiring deeper forming of the sealed pouch portion, thereby overcoming material forming depth limitations while accommodating larger battery capacity.
3Duration of action of moving object
If gas is produced during charging and discharging, then battery operation is maintained, but gas accumulation causes swelling and reduces battery performance
Solution Approach 1:
The unsealed openings in the extension portion convert the harmful effect of gas accumulation into a beneficial continuous venting mechanism. Gas produced during charging and discharging naturally escapes through the openings, preventing swelling and maintaining shape stability, while the extension portion's structure guides and controls this gas release process.
4Quantity of substance
If multiple batteries are stacked together, then energy density is improved, but heat transfer between batteries increases causing safety issues
Solution Approach 1:
The unsealed extension portion serves as a thermal intermediary and insulating barrier between adjacent batteries in a stacked configuration. It physically separates the heat-generating sealed pouch portions of neighboring batteries, reducing direct thermal coupling and heat transfer, thereby improving safety while allowing high energy density stacking.
Data Source
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AI summary
The present disclosure is directed to providing a secondary battery with fewer limitations on shape and improved battery capacity, and for preventing problems caused by gas produced during charging and discharging. The secondary battery according to an embodiment of the present disclosure includes an electrode assembly including a plurality of electrodes and a separator stacked parallel to each other, a sheet-type outer packaging having an internal space for accommodating the electrode assembly, and an outer packaging opening configured to communicate the internal space with an outside, and a cap configured to cover the outer packaging opening of the sheet-type outer packaging, wherein a height of the cap in a stack direction of the electrodes and the separator is larger than a height of the electrode assembly.