Galaxy Note 7 recall shows challenges of stronger batteries

SEOUL, South Korea (AP) — Samsung's recall of 2.5 million Galaxy Note 7 phones after several dozen caught fire and exploded may stem from a subtle manufacturing error, but it highlights the challenge electronics makers face in packing ever more battery power into ever thinner phones, while rushing for faster release dates.

Koh Dong-jin, Samsung's mobile president, said in announcing the recall on Sept. 2 that an investigation turned up a "tiny error" in the manufacturing process for the faulty batteries in the Note 7s that was very difficult to identify.

Samsung has not recalled Note 7s sold in China, but the company has refused to say which of its two battery suppliers made the faulty batteries or clarify whose batteries are used in which Note 7 smartphones.

The company also refused comment on South Korean media reports that it has stopped using batteries from Samsung SDI, one of its two suppliers, in the Note 7.

Problems with lithium batteries have afflicted everything from laptops to Tesla cars to Boeing's 787 jetliner, though having so many lithium-ion battery fires in a short time is unheard of, Park said.

The batteries are ubiquitous in consumer electronic devices, favored by manufacturers because they are lightweight and pack much more energy into a small space than other power cells.

[...] storing so much energy in a tiny space, with combustible components separated by ultra-thin walls, makes them susceptible to overheating if exposed to high temperatures, damage or flaws in manufacturing.

"There was no choice but to make the separator (between positive and negative anodes) thin because of the battery capacity," said Lee Sang-yong, a professor at Ulsan National Institute of Science and Technology who worked more than a decade at LG Chem, a leading lithium battery maker.

While Apple and Samsung are using built-in batteries for their premium phones, LG Electronics, Samsung's smaller South Korean rival