Battery Tab Resistance Gradient for Gas Venting
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Solution Overview
Problem
Lithium-ion batteries are prone to safety hazards such as short circuits and overcurrent charging, leading to excessive internal temperatures, fires, and explosions due to inadequate safety performance.
Innovation Solution
An electrochemical device design featuring a tab with a first region of higher resistance per unit length than a second region, where the tab adhesive melts to fail the top seal, allowing gas escape and reducing the risk of fire and explosion, utilizing materials like nickel, aluminum, and specific adhesive layer configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tab is made with uniform resistance throughout, then the electrical connection is stable and current distribution is even, but the safety response to overheating is insufficient and gas cannot escape timely
Solution Approach 1:
The tab is designed with different resistance characteristics in different regions: the first region (near the electrode assembly) has higher resistance while the second region (extending outward) has lower resistance. This local differentiation enables the high-resistance first region to heat up faster during abnormal conditions, triggering adhesive melting and seal failure for gas release, while the low-resistance second region maintains stable current conduction.
2Reliability
If the tab adhesive melting point is increased to maintain sealing integrity, then the seal strength is improved, but the gas cannot escape in advance during overheating events
Solution Approach 1:
The adhesive is formulated with a specific melting point range (80°C to 120°C) that is lower than the operating temperature of the battery. During normal operation, the adhesive maintains strong sealing. During overheating events, the adhesive melts at the controlled temperature to fail the seal and enable gas escape, thus converting the adhesive from a purely structural component to a safety-responsive component.
Solution Approach 2:
The adhesive's melting property, which could be seen as a weakness compromising seal integrity, is actually utilized as a safety mechanism. When overheating occurs, the adhesive melts to create a failure path for gas release, transforming the potential harm of seal failure into a beneficial safety response that prevents more severe explosions.
3Speed
If the resistance ratio R1/R2 is made very high to ensure rapid heating and adhesive melting, then the safety response speed is improved, but the current distribution becomes too uneven affecting normal operation
Solution Approach 1:
The first region is designed with moderately increased resistance (R1/R2 ratio between 1.5 and 12) rather than extremely high resistance. This partial increase is sufficient to create noticeable temperature difference and trigger adhesive melting under overheating conditions, while remaining low enough to maintain acceptable current distribution during normal operation, avoiding excessive power loss or heating during regular use.
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
The design enhances safety performance by facilitating early gas exhaustion and preventing critical temperature failures, thereby reducing the risk of fires and explosions in lithium-ion batteries.
Implementation Method 1
the first region in which a current flows can generate heat under assistance of the current and heats up faster than the second region
Implementation Method 2
the tab adhesive in the first region melts
Data Source
Figure 1~2d
Figure 3e~5
Figure 6~7
AI summary
An electrochemical device (100), in which a resistance of a first region (11) is increased by letting a resistance per unit length R1 of the first region (11) be greater than a resistance per unit length R2 of a second region (12), and by letting the two resistances satisfy 1.5 ≤ R1/R2 ≤ 12. Therefore, when an abnormality such as a short circuit or overcurrent charging occurs in the electrochemical device (100), the first region (11) in which a current flows can generate heat under assistance of the current and heats up faster than the second region (12). Therefore, the tab adhesive (2) in the first region (11) melts. A top seal between the tab (1) at the melted part and the housing fails. A gas generated by an electrolytic solution escapes from the failed part of the top seal, and the electrochemical device (100) achieves the gas exhausting effect in advance.