The trouble with Samsung’s phablet has been said to be everything from tension in the battery fabric tape to inferior batteries but hardware engineer Anna Shedletsky says that there many have been a fundamental flaw in the Note 7’s design that caused some batteries to explode.
To understand that flaw you first need to understand how a battery is composed.
The battery in the Note 7 was a lithium-polymer battery. Simply put that means there is a layer of lithium cobalt oxide (the positive pole) and a layer of graphite (the negative pole) which are separated by a polymer coated in electrolytes. The polymer allows energy to flow through it to the two poles without the lithium cobalt oxide and graphite touching.
If the two poles were ever to touch, they would explode.
And that is where Samsung’s folly sits according to Instrumental.
During its tear down the firm found that space that the Note 7’s battery had to play with was minuscule – bordering on non-existent in some cases.
“Samsung stated that these separator layers may have been thin to start with due to aggressive manufacturing parameters. Add some pressure due to normal mechanical swell from the battery or accumulated stress through the back cover (e.g. from being sat on in a back pocket), and that pressure could be enough to squeeze the thin polymer separator to a point where the positive and negative layers can touch, causing the battery to explode,” writes Shedletsky.
Indeed the space between the battery and the rest of the phone was less than 0.1mm in some places and non-existent in others.
“Our two-month old unit had no ceiling: the battery and adhesive was 5.2 mm thick, resting in a 5.2 mm deep pocket. There should have been a 0.5 mm ceiling,” says the Instrumental engineer.
The firm goes on to say that it is of the opinion that had the Note 7 note been recalled the tiny dimensions and a battery’s inherent nature to expand would have pushed the smartphone apart in a few years.
“The design and validation process for a new product is challenging for everyone,” says Shedletsky. “In this case, Samsung took a deliberate step towards danger, and their existing test infrastructure and design validation process failed them. They shipped a dangerous product.”[Source – Instrumental]