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How are the lithium batteries of our smartphones inside?

26 mayo, 2021

The batteries of our smartphones are, possibly, the most important element, because without battery the mobile does not work. In addition, it is the element that has evolved more slowly over the years, and time has not lacked. The fact is that, today, lithium batteries are responsible for powering our mobiles.

Other types of batteries are still being investigated, such as graphene, kevlar, and practically anything we can think of, but we have to settle for those of lithium ion (Li-Ion) and lithium polymers (LiPo). So it is time to find out what they are like inside and who is most responsible for making them.

What is a lithium battery?

Liion battery

First of all, as we have already mentioned above, there are two types of lithium batteries in our smartphones: lithium ion batteries and lithium polymer batteries. Although they have a number of similarities, they also they have their differences and reasons why a manufacturer may choose one or the other.

The main characteristic of lithium-ion batteries is to use a few lithium salts as a “bridge” between the positive pole (anode) to the negative pole (cathode) to allow the passage of energy that will give life to our device. In the case of lithium polymer batteries, the difference is that the lithium salt is contained in a polymer, or gel, to keep it safe from spills.

In both cases, when the battery is running low, lithium ions travel from the cathode to the anode through their “bridges” to supply the energy until all the ions are at the anode, it is at this moment that the battery is depleted. The ions travel in the opposite direction during charging (from anode to cathode).

Lithium-ion batteries are, today, the most used in our smartphones, but lithium-polymer batteries (which are actually lithium-ion polymer) They are frequently used in those devices that need a battery that must fit in not so rectangular spaces.

Such cases could be those of the terminals of the LG G Flex family (the battery is curved too) or the smartwatches, where due to their characteristics lithium ion batteries have no place.

How are they manufactured and where are the largest factories located?

The manufacturing process of a lithium battery begins with a lithium ingot that is usually about 5 kg, which is introduced into a press that crushes it until there is a sheet 200 meters long and 250 microns thick. After this, the sheet goes through a laminator which will further reduce the thickness, to between 20 and 40 microns, and will have a length of 2 km.

A machine winds the sheet for a number of turns (26 in the video for a battery intended for a hybrid car), then it is put into a vacuum oven, where the layers adhere. After this, the staff check that the 3.56V required and verified to be the exact thickness. If both tests pass, the batteries are ready for their final step..

This step consists of storing them, separated by metal plates, until it is time to metallize the contacts, when they are placed in a robotic container, which introduces the battery into a protective tank and spray molten metal to metallize the contacts. After this, the battery is ready to be inserted into the device for which it is intended.

If we focus on the main companies in the manufacture of lithium-ion batteries (the majority in mobile phones), we have Panasonic, Samsung SDI, LG Chem, ATL and Sony. Three of them, Samsung SDI, ATL and LG Chem are protagonists in the problem of defective batteries in Note 7 (SDI) and its solution (ATL and LG Chem).

How could a battery burn as it has happened with the Note 7?

Note 7 Explosives

The problem lies in lithium, which, at room temperature, it is highly flammable and slightly explosive if exposed to air or water, having special repercussion in the latter case. The reason why this element is used for mobile batteries is because of its extreme lightness being half as dense as water.

Lithium batteries are perfect for our mobiles (within the current options) thanks to their lightness, long useful life (can reach 1,000 charge cycles) and their greater charge capacity. They are also being used for hybrid cars and electric ones being clearly superior to traditional batteries.

So, going to the heart of the matter, what could be the problem with these explosions occurring on the Note 7s? If SDI (responsible for faulty batteries) has failed in the manufacturing process, allowing, in some way, air or water will eventually enter, it would not be unusual for this reaction to occur.

It is also possible that the battery suffered such heat that it caused an explosion of the same, and it is that these batteries, although in low temperatures they perform less, it is also not advisable to leave them exposed to heatAnd if SDI’s quality control has not been adequate, poorly manufactured batteries could explode at the least exposure to heat.

We can see examples like that of a person who says that his car burned when leaving his Note 7 charging inside, if the car has been exposed to heat, increasing the temperature inside, the explosive party is served. Or that of a 6-year-old boy whose mobile exploded in his hands while watching a video.

Regardless of whether I believe these cases or not (I am skeptical), if SDI has screwed up when manufacturing many of its batteries and, somehow, the lithium comes into direct contact with the air, can cause quite serious damage. However, for now there is no official detailed clarification (at the manufacturing level) regarding how this massive incident occurred.

For now we can only formulate theories and wait for Samsung to replace current devices with new ones manufactured by ATL and LG Chem, which until now were in charge of the Note 7 from China. Do you have any theory about what happened?

In Engadget | This is everything we know about faulty batteries in the Samsung Galaxy Note 7