Scientists in Stanford University have developed a "smart" lithium-ion battery that gives ample warning before it overheats and bursts into flames. The battery is designed for conventional lithium-ion batteries now used in billions of cellphones, laptops and other electronic devices, as well as a growing number of cars and airplanes.
Lithium-ion batteries can destroy devices when they overheat, and while these cases rarely occur, they still pose a huge problem. In addition to smartphones, this issue affects laptops, e-readers, cars, planes and other machines powered by a lithium ion battery. Boeing grounded a 787 fleet in 2013 after the lithium-ion batteries on the plane caught fire.
These batteries come with a lithium oxide cathode and a graphite anode, which are separated by a thin, porous polymer sheet designed to let ions move between the two electrodes, Science Now reported. Overheating and catching fire can occur when a lithium-ion cell overcharges, leading to tiny chains of lithium called "dendrites" coming out of the anode and piercing through the polymer separator and touching the cathode. This can lead to an electrical current moving through the dendrites to the cathode to short-circuit the cell.
The research team's "smart" separator consists of a 50-nanometer thin layer of copper placed between two polymer sheets. The copper layer is connected to a third electrode in order to measure voltage. The voltage between the anode and the copper layer goes down to zero when the dendrites get to the separator. This alerts smartphone users that they should change their battery while it is still working safely, which gives them a chance to avoid the battery exploding
Manufacturing defects, such as particles of metal and dust, can pierce the separator and trigger shorting, as Sony discovered in 2006. Shorting can also occur if the battery is charged too fast or when the temperature is too low — a phenomenon known as overcharge.
The copper layer acted like a sensor that allows you to measure the voltage difference between the anode and the separator. When the dendrites grow long enough to reach the copper coating, the voltage drops to zero. That lets you know that the dendrites have grown halfway across the battery. It's a warning that the battery should be removed before the dendrites reach the cathode and cause a short circuit.
You might get a message on your phone telling you that the voltage has dropped to zero, and the battery needs to be replaced and the early-warning technology can also be used in zinc, aluminum and other metal batteries. "It will work in any battery that would require you to detect a short before it explodes.
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