A BETTER BATTERY

摘要

The mobile world depends on lithium-ion batteries - today's ultimate rechargeable energy store. Last year, consumers bought five billion Li-ion cells to supply power-hungry laptops, cameras, mobile phones and electric cars. "It is the best battery technology anyone has ever seen," says George Crabtree, director of the US Joint Center for Energy Storage Research (JCESR), which is based at the Argonne National Laboratory near Chicago, Illinois. But Crabtree wants to do much, much better. Modern Li-ion batteries hold more than twice as much energy by weight as the first commercial versions sold by Sony in 1991 -and are ten times cheaper. But they are near-ing their limit. Most researchers think that improvements to Li-ion cells can squeeze in at most 30% more energy by weight (see 'Powering up'). That means that Li-ion cells will never give electric cars the 800-kilometre range of a petrol tank, or supply power-hungry smart-phones with many days of juice.