Update: See the end of this article for Samsung's findings on what happened.
Speculation abounds as we wait for Samsung's official report to come out regarding the cause of the Note7's untimely demise, but a recent teardown from Instrumental (done with fire extinguisher in hand) shows a critical design flaw that could be the cause the rash of explosions and fires associated with the phone.
Instrumental, a company that specializes in assisting companies with detecting and fixing issues with their products, found that Samsung had violated a key engineering principle in designing a handset: Not accounting for battery bloat.
Lithium polymer batteries naturally expand as they cycle through charges and depletion. Engineers have to account for this and leave ample room within the battery compartment (usually about 10% of the battery's total size for ceiling clearance) for the battery to safely swell into.
The Note7's 3,500 mAh battery was literally crammed into the phone with incredibly little room for the battery to breathe. In fact, the researchers theorized that their test unit was itself under pressure, as it had no ceiling clearance against its rear housing.
Having the battery entombed in a rigid pocket of CNC-machined aluminum and glass proved to be a recipe for disaster. The Note7's battery would sometimes squeeze into itself as it had nowhere to go, and apply undue pressure to its already thin cell walls that separate negative and positive layers. Excess heat is created when the layers rub against each other and, in some cases, it can get hot enough to set the phone ablaze.
The report goes on to make a damning assertion:
...Samsung took a deliberate step towards danger, and their existing test infrastructure and design validation process failed them. They shipped a dangerous product. That this is possible at one of the top consumer electronic companies in the world is humbling
This certainly won't be the last time we here of this issue. Samsung has yet to publish an official report regarding the Note7's untimely demise, and we should hold off on drawing any final conclusions. We will keep you updated with any future news, especially when Samsung releases official results of its investigation into the matter.
Samsung has revealed the findings of their investigation and have concluded that batteries from both themselves and a third-party were the cause of the fires—not because of limited space in the phones to accommodate "bloat" from the batteries. You can see their results in the infographic below.