The cause of the Note 7 battery failures seemed like a mystery ever since the first reports started pouring in back in September. Samsung stated that they didn’t even know what the cause of the issue was, and that was as disheartening as anything can get. Well, a new tear down from Instrumental has revealed to us the cause of the explosions. What was originally thought to be the cause was some sort of engineering misstep made by Samsung SDI, the Samsung subsidiary that produced 70% of the batteries for the Note 7. That all changed when new units, not built by the SDI, also started catching fire. What the tear down revealed to us is that it wasn’t SDI’s fault, but Samsung’s fault.
Without getting too much into the chemistry of lithium ion batteries, there are two fundamental materials in inside of a cell: a positively charged layer of some sort of lithium oxide (a cathode), and a negatively charged layer of some sort of carbon (an anode). There’s an electrolyte which allows electrons to be transferred freely between these materials and a separator, which keeps these materials from physically touching. It’s curtail that the positive and negative layers don’t come into contact with one another, as this causes a chemical reaction which results in the explosions. So what happened? Well, when a battery charges and discharges, it expands and contracts. In order to deal with this, there’s a space between the battery and the walls and ceilings of the battery housing when it can expand and fill. The problem is that there just wasn’t sufficient space put between the battery and the wall for the Note 7. Now, think back to the reports of explosions- they were all stating that the phones caught fire while charging. These batteries expanded to the point where pressure built up inside. This pressure caused the separator layer to be punctured and the positive and negative layers came into contact with each other. When they touch, the electrons flowed directly into the electrolyte, causing it to heat up at a rapid rate. This heating, of course, causes the fire. There was space built into the battery compartment, but it just wasn’t enough. There was absolutely no space between the top of the battery and the ceiling of the housing. The “Rule of thumb” is at least 10%, meaning there should have been a space above the battery measuring at least 10% of the thickness of the battery- so about .5mm. The space between the battery and the walls was also miniscule (as you can see in the picture below). This all contributed to the battery failure.
It’s not hard to turn a judgmental eyes towards Samsung for this. It was an attempt to maximize the capacity of the battery without adding any unneeded girth to the device. While the battery was housed in a CNC casing, the problem proved to beyond its capabilities. Samsung ignored a basic safety rule and this shows that small things can indeed have major consequences. Suffice to say that the company has been through enough with this whole fiasco, but it still stands that this could have been avoid easily. While the company is setting up to launch the Galaxy S8, let’s just hope that they learn from their mistakes.
For more news like this be sure to: