Batteries Last a Week After 15-Minute Charge
Imagine if your phone's battery could hold a single charge for a week after being plugged in for only 15 minutes. According to some engineers at Northwestern University, this is no stretch of the imagination. They've created an electrode for lithium-ion batteries that extends their lasting life by ten times after only charging them for one-tenth of the time it normally takes.
"We have found a way to extend a new lithium-ion battery's charge life by 10 times," wrote Harold H. Kung, in a paper published in the journal Advanced Energy Materials. Kung is professor of chemical and biological engineering at Northwestern's McCormick School of Engineering and Applied Science. "Even after 150 charges, which would be one year or more of operation, the battery is still five times more effective than lithium-ion batteries on the market today."
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Lithium-ion batteries in our devices have two major flaws: limited energy capacity and a slower-than-molasses recharge rate. This electrode eliminates these problems. Here's how:
When you're charging your device, lithium ions are being sent back and forth from the ends of the battery — the anode and the cathode. When all the ions make it to the anode, the glass is full, so to speak. Once you start using your device, the ions begin trickling back to the cathode until your battery is dead.
Because the anode can only accommodate one lithium atom for every six carbon atoms, battery charge density is hindered. Scientists have tried replacing the carbon with silicon because it can accomodate more lithium. But silicon expands and retracts during charging, which causes the battery to lose its charge very quickly.
Kung and his colleagues solved this problem by sandwiching the silicon between sheets of graphene, which is a form of carbon. This stabilized the silicon and maximized the amount of lithium ions that could travel between the two sheets.
Kung's team also sped up the recharge rate by poking microscopic holes in the graphene sheets. This gave the ions a shorter secondary route to the anode, drastically reducing charge times by 10 times.