text: Samsung has permanently stopped production of the Galaxy Note 7 less than two months after its release, as the phone caused hundreds of reported fires and explosions worldwide.
  Its flagship smartphone - which retailed at £739 and was initially hailed as one of the best phones of 2016 - issued a global recall of the water-resistant phones, including "safe" replacement devices, amid overheating fears.
  Samsung has not confirmed the number of incidents, but estimates suggests that fewer than 150 handsets have overheated and, in some cases, caught fire.
  Here are circumstances that can cause a handset to overheat.
  What is a lithium-ion battery?
  Samsung have traced the issue to a 'faulty battery'. The model uses lithium-ion batteries for power. There are three parts to these batteries: the anode, cathode and a lithium electrolyte.
  The anode and cathode are the positive and negative terminals, and the electrolyte is a highly flammable chemical liquid in between them that conducts electricity.
  Both elements work with the electrolyte but the anode and cathode are separated by a porous physical barrier, called the separator, to prevent them connecting.
  The battery creates electricity by driving electrons through a circuit to the anode until all of the electrons within the smartphone are transferred to the anode.
  When a smartphone is plugged in to charge, electricity resets a chemical reaction within the battery, moving electrons back from the anode to the cathode.
  Lithium ion batteries are commonly used in devices such as laptops and phones because they are small, light, store energy efficiently and are slow to lose their charge.
  So, what causes overheating?
  Lithium is a highly volatile substance, so any number of changes can cause the liquid to overheat.
  One report by Korea's Agency for Technology and Standards found that the Note 7 had a manufacturing error which "placed pressure on plates contained within battery cells," bringing “negative and positive poles into contact."
  When the anode and cathode touch it can trigger a "thermal runaway."
  When a battery's temperature hits around 100C (200F), its materials begin to break down. This starts a chemical chain reaction that releases its own energy and accelerates the heating in a snowball effect.
  In a “thermal runaway", the temperature can keep increasing until the battery catches fire.
  Packing it in
  Most mobile phone batteries are created by pushing together a stack of battery components. However, a battery can only produce as much electricity as its chemical components can store.
  One of the only ways to increase battery life, a high demand in the smartphone industry, is to increase the size of the battery but, as thin smartphones are also in vogue, this can cause tightly packed components.
  Charging causes the battery to heat and, if this heat is not released from the phone at a sufficient speed, it can catch fire. A rammed smartphone may stop heat from escaping.
  Fault or damage
  If the battery overheats, lithium plates can also collect around the anode creating a short circuit and potentially punctures the casing or separator. This can cause the fluid to leak into other components of the phone and set alight.
  Similarly, if unwanted materials, like scraps of metal, accidentally end up inside the battery during production, they can short circuit the battery and set off a thermal runaway.
  Dropping a device may also cause a break in the separator between the anode and cathode which, again, can trigger a thermal runaway.
  If voltage levels or the input current from the mains plug are not controlled, this can cause overheating.
  This can happen when the “battery management system” — which monitors the electrical current and normally instructs a chip inside the phone to stop the current when a battery is fully charged — fails or is faulty.
  This may help to explain why, upon the news of the overheating, Samsung issued a software update that limited the charging capacity of Note 7 phones to a maximum of 60 per cent.
  Has it happened before?
  Other phones have suffered a similar fate. In 2009, Nokia recalled 46 million phone batteries after it was found that some of them were short circuiting. In 2010, 2015 and 2016 there were rare reports of Apple iPhones catching fire. And last month, a six-year-old boy was rushed to hospital in New York to be treated for burns to his body after a Samsung Galaxy Core caught fire in his hands.
  Why is the Note 7 different?
  Although a lot of devices use these batteries, and there have been exploding phones in the past, the number of reports of the Note 7 overheating are substantial.
  Reports suggest that the fault in the phones could have been caused by Samsung rushing the production of the Note 7.
  In a bid to outstrip sales of Apple's iPhone 7 and 7 Plus, Samsung allegedly put pressure on its engineers to deliver the Note 7 under tight deadlines and with little sleep.
  "Clearly, they missed something," said Anthea Lei, a Bloomberg Intelligence analyst. "They were rushing to beat Apple and they made a mistake."