Any electronic device with a battery will gradually discharge, even if it is completely switched off. As it turns out, one of the reasons for this is an amazing and very common manufacturing defect identified by researchers from Halifax, Canada.
According to Michael Metzger, associate professor at Dalhousie University, this is a completely unexpected phenomenon that no one would have thought of. The problem lies in the use of tiny pieces of plastic tape used to secure battery components.
As you know, batteries give off energy due to chemical reactions happening inside them. Every battery consists of an anode, a cathode and an electrolyte (liquid or paste/gel). When the battery is connected to devices, electrons move along the electrodes, powering smartphones, laptops, and other devices. Problems arise when the electrons do not move along the electrodes/cables, but within the electrolyte from one electrode to the other, which leads to a discharge without the slightest external load – therefore even switched-off devices lose charge.
In their search for the perfect battery, the researchers used batteries in a very warm environment – at 85 degrees Celsius – under such conditions batteries usually lose their useful properties much more quickly. During one of the tests, the electrolyte turned red, which actually shouldn’t have happened because the battery is a closed system – something happened in it.
As a result of chemical analysis, it turned out that dimethyl terephthalate (DMT) impurities appeared in the electrolyte, which caused the batteries to spontaneously discharge. It turned out that DMT is structurally similar to a molecule of polyethylene terephthalate (PET) – the latter is used to make plastic bottles, food containers, etc. And also for connecting battery components. Almost microscopic pieces of plastic penetrated the electrolyte and caused chemical reactions, which means that the battery gradually self-discharged. It is noteworthy that this material is widely used by battery manufacturers.
After Metzger and his team shared the discovery in November 2022, many computer and electric vehicle manufacturers took an interest in the information. According to scientists, many companies are already ready to replace such components in their batteries in order to avoid rapid self-discharge.
Scientists have already proposed a solution – instead of PET, use a slightly more expensive, but no less common material – polypropylene, which is used to create more reliable plastic goods and is more resistant to chemical attack.