Why Galaxy Note 7 batteries exploded, finally revealed

A teardown of the now discontinued Galaxy Note 7 has found that its explosion fiasco was due to an 'aggressive' design push by the company that caused its battery to compress beyond what it could sustain.

Instrumental, a company that makes engineering tools has conducted teardowns of such devices. It examined a Galaxy Note 7 and found that the problem was not with the battery alone as earlier claimed by the company. Samsung had first blamed its sister subsidiary Samsung SDI's lithium polymer battery for the problems, but new models that contained batteries from other suppliers like China's ATL also met a similar fate.

The teardown shows that the phone had been designed in such a way that it could compress the battery even during normal operation.

Explaining why this can create problems, the report says the lithium-polymer battery in the Note 7 is a flattened "jelly-roll". This consists of a positive layer made of lithium cobalt oxide commonly used in lithium-ion batteries, a negative layer made of graphite, and two electrolyte-soaked layers made of polymer. This separator is crucial as it allows ions to flow between the positive and negative layers without them physically touching each other. However, if the positive and negative layers touch, the energy goes directly into the electrolyte. This results in heating the electrolyte, and in this case, there was more energy flow resulting in more heat and consequent explosion.

According to the report, these separator layers were too thin to sustain the pressure. If a smaller battery was used, it would not have met the same fate but would have reduced the system's battery life below the level of Note 5, the model it was aiming to not only succeed but outdo. Additionally, the battery would be small compared to the iPhone 7 Plus, one of the iPhone models Samsung was aiming to take on this year.

The company is expected to reveal its official version of why the Note 7 fiasco happened sometime this month.