Samsung could have avoided the Note 7’s battery issue, according to the results of a new teardown by Instrumental, a manufacturing software startup.
The teardown reveals that the Note 7’s engineering and design team did not leave enough internal space for the handset’s 3,500 mAh battery to expand.
The Note 7’s battery is housed within a machined compartment that only allows between 0.1 mm and 0.5 mm of space for expansion. Over time and many recharge cycles, lithium-ion batteries swell and change shape. With not enough room to expand, excessive pressure is likely what caused the Note 7’s battery to catch on fire in many circumstances.
The Note 7’s battery features two electrolyte-soaked polymer layers. Under normal circumstances, these layers allow ions to pass between the battery’s positive lithium cobalt oxide layer and its negative graphite layer without the two components touching one another. In the case of the Note 7’s battery, the polymer layers likely became compromised after a number of battery cycles, allowing the positive and negative layers to touch, in turn leading the entire battery to overheat and, in some cases, explode.
In engineering the Note 7’s battery compartment, Samsung’s engineers failed to follow the best practices of their trade.
According to Instrumental, it’s common practice to leave some space above the battery to allow it to expand — 10 percent of the battery’s height is a baseline, says the website. In designing the Note 7’s battery compartment, Samsung failed to observe this rule. Instrumental speculates this was intentional as Samsung wanted to maximize the battery’s capacity.