Pouch Cell Sealing Grooves for Colloid Overflow and Gas Venting
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Solution Overview
Problem
Soft pack lithium-ion batteries face safety risks due to overflow of sealing colloid during hot pressing, which can cause compression and puncture of electrode plates and separators, leading to potential safety hazards.
Innovation Solution
The electrochemical apparatus incorporates a sealing colloid with a first groove on its surface to collect molten colloid and a second groove that communicates with the accommodating cavity, allowing gas expansion during thermal events to flush away the sealing portion, thereby preventing explosions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hot pressing is performed to seal the tab-side package bag, then sealing is achieved, but molten colloid overflows and causes safety risks
Solution Approach 1:
A groove structure is introduced as an intermediary element between the sealing colloid and the electrode assembly. The groove receives and contains the molten colloid during hot pressing, preventing it from directly contacting and damaging the electrode assembly, thus resolving the contradiction between achieving reliable sealing and preventing colloid overflow damage
Solution Approach 2:
The harmful molten colloid overflow is converted into a beneficial sealing mechanism. The groove guides the molten colloid to flow into a controlled position where it can effectively seal the tab-side package bag, transforming the potential hazard into a useful sealing function that enhances both sealing reliability and safety
2Strength
If the package bag is sealed tightly, then sealing strength is improved, but gas expansion during thermal events cannot be released, leading to explosion risks
Solution Approach 1:
The sealing structure is segmented into multiple functional zones: a sealed portion for maintaining sealing strength, an inner unsealed portion with a groove for gas accumulation, and a communication groove connecting to the external environment. This segmentation allows the system to simultaneously achieve strong sealing under normal conditions and safe gas release during thermal events
Solution Approach 2:
The groove structure is pre-designed and built into the sealing colloid before thermal events occur. When gas expansion happens during thermal runaway, the groove is already in position to receive and guide the expanding gas, enabling immediate and effective pressure relief without requiring additional active components
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively reduces the risk of colloid overflow and electrode damage, enhancing safety by containing the molten colloid and facilitating gas discharge during thermal events, thus preventing explosions.
Implementation Method 1
typically a tab colloid and a package bag on a tab are hot pressed to implement sealing of a tab-side package bag. In a hot pressing procedure, under an effect of high temperature and pressure, the tab colloid melts and the molten tab colloid flows around
Implementation Method 2
When a hot-box test is performed on the electrochemical apparatus or thermal runaway occurs, the gas being heated in the accommodating cavity expands. Some of the gas converges in the second groove and impacts the sealing portion in a concentrated manner in the second groove, so that the sealing portion can be flushed away and the gas in the accommodating cavity can be discharged
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
An electrochemical apparatus including an accommodating member, an electrode assembly, a metal strip, and a sealing colloid. The accommodating member encloses an accommodating cavity (11) for accommodating the electrode assembly (20). The metal strip (30) has a first part (21) extending out of the accommodating member, a second part (32) provided with the sealing colloid (40), and a third part (33) located inside the accommodating cavity (11) and electrically connected to the electrode assembly (20). The sealing colloid (40) includes a sealed portion (41) connected between the accommodating member and the second part, along with the accommodating member forming a sealing portion of the electrochemical apparatus (100); and an inner unsealed portion (42) provided in the accommodating cavity (11). The inner unsealed portion (42) is provided with at least one first groove (421) and at least one second groove (4221), and the second groove (4221) is in communication with the accommodating cavity (11).