NEWS
Understanding Edge Voltage in Pouch Lithium Batteries
Release time:
2024-08-14
Edge voltage is the voltage difference between the battery tabs (positive or negative) and the aluminum layer of the aluminum-plastic film.
Definition: Edge voltage in pouch lithium batteries refers to the voltage between:
The positive tab and the aluminum layer of the aluminum-plastic film.
The negative tab and the aluminum layer of the aluminum-plastic film.
Theoretical Consideration: In theory, the positive tab and the aluminum layer of the aluminum-plastic film should be insulated from each other, meaning their voltage difference should be zero. However, during the manufacturing process, the PP (polypropylene) layer inside the aluminum-plastic film may sustain localized damage, resulting in partial conductivity (including both electron and ion channels). This creates a micro battery, leading to a potential difference (voltage).
Industry Standards: The standard for edge voltage varies among manufacturers, but it is generally set below 1.0V, based on the dissolution potential of lithium-aluminum alloys.
Edge Voltage Testing: Edge voltage testing is crucial for evaluating the effectiveness of the packaging in lithium batteries, particularly in detecting short circuits between the battery tabs and the aluminum-plastic film. Short circuits can lead to aluminum foil corrosion, electrolyte leakage, swelling, low voltage, and other safety risks.
Specifics for Lithium Polymer Batteries: Edge voltage specifically refers to the voltage between the positive tab and the aluminum layer of the aluminum-plastic film in pouch lithium batteries. While these components should be insulated, manufacturing defects can cause the PP layer to break down, allowing for partial conductivity and the formation of a micro battery, creating a potential difference. Most industry standards set the edge voltage below 1.0V, based on the dissolution potential of lithium-aluminum alloys.
The Role of Potential Difference: The potential difference between the positive tab and the aluminum layer helps detect whether an electron channel exists between the negative tab and the aluminum-plastic film. If such a channel exists and the PP layer is damaged, corrosion may occur.
Swelling Due to Corrosion: Swelling is a particularly troublesome issue. Without effective detection methods, defective products may reach customers and exhibit swelling after several months, leading to returns. This swelling often results from the aluminum-plastic film being corroded, allowing moisture to penetrate and react with the electrolyte inside the battery.
Why Control Edge Voltage? Controlling edge voltage is essential because a damaged PP layer in the aluminum-plastic film can lead to corrosion and reduced battery capacity. Corrosion requires two conditions:
An electron pathway between the negative tab and the aluminum layer of the aluminum-plastic film.
An ion pathway between the aluminum layer and the electrolyte.
Both conditions must be met for corrosion to occur. Once both pathways are established, lithium ions react with the aluminum layer to form lithium-aluminum alloy, a powdery substance that penetrates the aluminum-plastic film, creating visible black spots. These spots become more pronounced over time and with repeated charging cycles.
Detection Methods: The following methods are commonly used for detection:
Resistance Testing: Measure the resistance between the aluminum-plastic film and the negative tab. A resistance greater than 5 MΩ is generally considered safe. However, each company may define its own standard based on acceptable defect levels.
Current Testing: Measure the current between the positive tab and the aluminum layer using a DC source. A current exceeding 0.001 mA is typically considered defective.
Voltage Testing: Measure the voltage between the positive tab and the aluminum layer. A voltage greater than 1V is usually deemed defective.
These methods help identify and isolate defective products, ensuring only high-quality batteries reach the market.
Relevant information
Main office: Room 501, Building 3, No. 81, Dingye Road, Tangjiawan Town, High-tech District, Zhuhai City, Guangdong Province, China 519000
Manufacturing Center：Zhongneng Science Park, No. 168, Tanlong North Road,Tanzhou Town, Zhongshan, China
R&D and Sales Center in Oxford, UK：47,The Lawns, Kennington Road,Radley,Oxfordshire, UK, OX14 2JR
SAF Coolest v1.3.1.2 设置面板 GAGSD-ZGYF-JFAVE-ZQZ
无数据提示
Sorry, the current column is being updated, please look forward to it!