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Promise of lithium batteries – The Hindu: Mobile Edition

Lithium (Li), the lightest metal known, is what dreams are made of. It is part of the batteries in cell phones, sensors in medical devices, laptops, automobiles, defence equipment and aircrafts. Bolivia dreams of building its economy on its Li deposits. But is lithium-ion battery a ‘dream deferred’?

Li-ion battery is in the news because of two incidents in the Boeing 787 Dreamliner aircraft. There was a fire in one aircraft parked in the airport and in the other smoke was detected after take-off. The US Federal Aviation Administration issued a directive to ground these planes and the National Transportation Safety Board is doing a complete investigation. Other countries, including India followed suit and grounded these planes at a considerable financial loss.

Li-ion batteries are reliable and their failure rate is 1 in 10 million cells. Yet fires and recall of equipment do occur due to battery failure. A battery contains several cells. Each cell consists of a cathode, an anode and a separator between the two, electrolyte and current collectors. The cell generates power due to the motion of Li-ions. The anode is graphite containing Li. A typical cathode (and the one used in dreamliner battery) is made up of lithium cobalt oxide. The electrolyte contains lithium salts in an organic solvent, which is flammable. This is because Li reacts with water violently.

Li-ion battery delivers high power per volume or weight to start a jet engine fast. It delivers 250- 340 Watts/ kg compared to 150 W/kg of nickel-cadmium (Ni-Cd) battery. This also occupies less space because its energy density is 250-620 Watt hour per litre compared to 50-150 Watt hour per litre of Ni-Cd.



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