Leakage can cause various problems in lithium batteries, such as electrolyte evaporation, water infiltration, swelling, etc., which can lead to a decrease in battery performance and even fire and explosion. Perhaps in the impression of many people, the leakage performance of digital lithium batteries with small volume and capacity is not so obvious, and they even believe that even if they leak, there will not be any major problems, so they have not received much attention from the industry.

However, with the rise of the power battery market and the significant increase in downstream car companies' requirements for the performance of power batteries, especially safety performance and energy density, leakage issues have become increasingly important to power battery companies.

The current leak detection methods used in the lithium battery industry mainly include water visual leak detection (bubble detection method), air tightness leak detection (gas detection method), pressure drop leak detection (pressure drop method), differential pressure leak detection (differential pressure method), flow leak detection (flow method), and vacuum box helium leak detection (helium mass spectrometry leak detection method). Among these methods, helium mass spectrometry leak detection has the highest detection accuracy, which is 3-4 orders of magnitude higher than the leak detection accuracy of existing detection equipment in enterprises.

However, it is strange that traditional leak detection methods such as water bubble and gas detection are still widely used by domestic battery companies. Only a few large power battery companies such as CATL and BYD started using helium detection equipment for process testing a few years ago, and only a few are still using helium detection equipment to this day.

Since it is necessary to improve product quality, why are there so few power battery companies currently using helium detection equipment? What are the technical and marketing challenges? What is the future development trend?

Advantages of helium detection equipment compared to traditional leak detection methods

Helium detection involves first removing the air from the battery, then injecting helium gas, and using a helium mass spectrometer to detect any helium leakage. On the one hand, helium is an inert gas that does not react with positive and negative electrode materials, electrolytes, etc., making it very safe; On the other hand, helium is smaller than any other medium, and if even helium does not leak inside the battery, it indicates good sealing.

There are two helium testing methods that battery manufacturers can choose from: one is intermediate testing, which involves leak detection before the battery is dried and filled with liquid; One type is finished product inspection, usually conducted after chemical formation to detect leaks, and ultimately helium gas will remain inside the battery. Due to the characteristics of helium, it has more advantages than leaving air inside the battery and will not affect any performance of the battery, including safety.

Nowadays, due to different processes, some companies choose intermediate inspection while others choose finished product inspection. In fact, after intermediate inspection, leakage may still occur in the finished product because the injection port has not been detected at this time. And the finished product inspection includes testing even the last injection port of the battery, which will provide more assurance. Some battery factories are very rigorous and conduct both intermediate and finished product inspections, resulting in more sophisticated processes. This means that a battery production line is equipped with two sets of helium detection equipment.

Compared to traditional leak detection methods, helium detection has high detection efficiency, 3-4 orders of magnitude higher leak detection accuracy, and will not have any impact on the battery. However, the current positive pressure bubble leak detection method commonly used in the lithium battery industry can easily cause deformation of the battery shell, and the detection efficiency and accuracy are low, especially for metal shells and aluminum-plastic film flexible packaging lithium-ion batteries.

Acceptance level of helium detection equipment by power battery companies

Helium detection equipment can indeed help battery factories overcome potential risks and strictly control battery leakage issues. At present, large power battery companies have begun to gradually tighten battery leakage standards, and power battery companies like CATL and BYD are basically using helium detection equipment. In fact, the earliest use of helium detection equipment can be traced back to 2011, when it was attempted as a process.

It should be noted that although battery manufacturers are increasing their requirements for leakage accuracy, there is currently insufficient research indicating to what extent battery leakage will affect performance, and there are no relevant national standards in place. If the battery factory increases its investment in basic equipment too much, it is not appropriate. However, if leakage issues are subjectively ignored or low requirements are set, it may have an impact on battery performance and safety. Therefore, battery factories need to strike a balance between the two.

As an emerging industry, the lithium battery industry may not have all realized the importance of preventing battery leaks, nor may it have given sufficient attention. As a professional provider of helium detection equipment, Bowei Optoelectronics is committed to providing technical support and assistance to the lithium battery industry with "professionalism". The company's equipment can be flexibly set according to the leakage standards of battery enterprises.

Helium testing is suitable for various types of batteries in China

At present, helium detection is suitable for square aluminum shell and cylindrical aluminum shell batteries. As a producer of square aluminum shell batteries in China, most of the batteries currently using helium testing are square aluminum shell batteries. Any battery factory that produces this type of battery is starting to consider using helium testing. Manufacturers of cylindrical aluminum shell batteries are gradually starting to use helium testing.

The battery factory that produces cylindrical steel shells 18650 believes that low leakage can be ensured through the process, so helium testing is not necessary. The reason why soft pack batteries do not require helium testing is that they are covered with a layer of soft material on the outside, resulting in a very small pressure difference between the inside and outside, which prevents gas from coming out, leading to the lack of a good solution at present.

The cost of helium detection equipment will not increase the cost burden on battery factories

Nowadays, the processes of various battery factories are different, and their production efficiency and battery models are also different. Bowei Optoelectronics will provide customized equipment according to the production line arrangement and logistics docking method of the battery factory, and the corresponding quotation will vary. Compared to the overall equipment investment in battery factories, the investment in helium detection equipment is relatively small.

The demand for helium detection equipment in the future battery industry is growing

From the perspective of improving product quality, battery factories will pay more and more attention to helium testing, and overall demand is definitely increasing; From the perspective of leak detection technology, it should be possible to provide * * technical solutions for various types of batteries in the end. Therefore, regardless of which technology direction battery manufacturers choose in the future, overall demand will increase.