How Samsung screwed up

A highly technical explanation of Note 7 problems boiled down to the relatively large batteries not fitting well into the phones, and not enough insulating material inside.
In batteries by one manufacturer likely Samsung SDI used in the phones in the initial Note 7 recall, inspectors found damage to upper corners. That, combined with thin separators and high energy density, caused the phones to overheat. The cell-pouch design of the battery did not include enough room to safely accommodate its electrodes another flaw.
It was unclear to what extent the battery maker was responsible for those problems: Samsung said only that it had provided targets for the batteries.
We suggested that the Note 7 has innovations and a compact design and a 3500 mAh (battery) but we did not know how to make the separators within (the battery) or how many millimeters thick they should be, Koh told reporters.

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In other batches of batteries from a second manufacturer, presumably ATL, the researchers found welding defects and a lack of protective tape in some battery cells.

Though it faulted the batteries from its suppliers, Samsung said in a statement we provided the target for the battery specifications for the innovative Note 7, and we are taking responsibility for our failure to ultimately identify and verify the issues arising out of battery design and manufacturing.

Koh said Samsung would treat the event as a chance to strengthen the safety of lithium-ion batteries for the entire industry, not only us.

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