Exploding batteries: A serious charge

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With Samsung looking at a $4 billion-plus hit due to the Galaxy Note 7's explosive lithium-ion battery problems, how are the alternative technologies shaping up?

Phone companies often talk about bang-per-buck, but rarely mean it literally. Explosive devices are unpopular outside battle zones, so when the Galaxy Note 7, Samsung's now-discontinued flagship smartphone, started to combust in appreciable numbers, something was obviously wrong. The culprit proved to be the lithium ion (Li-ion) battery -- unsurprisingly, as that component stores the energy needed to run all the advanced electronics, high-speed radio links and large, bright screen that characterise today's top-tier handsets.

It's at this point that physics, marketing and expectation come into conflict. Users expect more brightness, more processing power and more features with every phone generation, but are not prepared to trade off phone slimness or life between charges. The Galaxy Note 7 battery stores 3,500 milliamp-hours (mAh), which at 3.7 volts checks in at around 13 watt-hours (Wh) -- all in a very slim, light package. That might not sound much, but Li-ion batteries are very good at accepting and delivering power quickly, which is what makes them the default technology for electric cars such as those made by Tesla.

It's not such a good idea in the trouser department. If all the power in a fully-charged Note 7 battery was used up in ten seconds, it would clock in at 4 kilowatts, which is the equivalent of several hundred bunsen burners in your pocket. As Li-ion batteries contain pressurised, combustible materials, the result of an internal short circuit -- when the battery will indeed do its best to produce as much energy as quickly as possible -- are spectacular. This is probably what happened in the Galaxy Note 7, due to distortions produced in the battery by the case, although we await the final report.

This, of course, is unacceptable, even if the fault occurs one time in a million -- the sort of level that in any other component would be hard to detect even by statistical' analysis. With tens of millions of some units in the field, and social media able to fan the flames, it doesn't take much to kill a product.

Image: ZDNet / Data: BatteryUniversity.com

Li-ion batteries were considered too dangerous for general consumer use when first invented in the 1970s. However, lithium is a superb material for batteries -- it's the lightest metal, with excellent electronic properties -- and after considerable work on safe construction and use, Sony produced the first consumer-grade batteries in 1991. All early Li-ion batteries used a liquid electrolyte -- the medium that allows ions to move between electrodes and thus electricity to flow. In 1994, the first economic polymer electrolyte matrix was announced, which is much safer, better able to be formed in different shapes, and increases energy density without increasing volume. Even so, it took until 2009 before the first lithium-polymer (Li-poly) batteries appeared in consumer products.

Given that lithium-based batteries have attracted by far the most investment and commercial interest in the mobile power market, it's clear that significant improvements in battery technology take a long time to reach production. With Li-ion technology still improving at around five percent a year, alternative approaches face a fearsome challenge. But as Samsung has learned to its cost, today's batteries are far from perfect.

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