"Smart" Lithium-Ion Battery Warns Before It Explodes

News of exploding smartphone batteries might be sensational but they are no light matter. Aside from the harm, or even death, that could come from those, they also point to a problem with lithium-ion batteries that exhibited elsewhere. While little can be done for a battery that explodes due to severe damage, in most other cases, accidents could be prevented if users knew that the battery is on the verge of combusting. That is what Stanford associate professor Yi Cui and other professors have sought to accomplish with this new "smart" battery.

Lithium-ion batteries are practically made up of two packed electrodes: an anode made of carbon and a cathode made of lithium metal-oxide, separated by an ultrathin polymer. The problem starts when the polymer, which is porous by nature, gets pierced by something, either by impurities inside the battery or through overcharging, which causes the lithium ions to pile up into long chains called dendrites. A pierced polymer would cause the battery to short and to eventually burts into flames.

The solution that the Stanford researchers came up with is to introduce another layer on top of the polymer on the anode side. This layer, made of copper, practically serves as a third electrode. It measures the voltage between the anode and the polymer separator. When dendrites reach the copper layer, it will drop the voltage to zero, signaling that the polymer layer is in danger of being pierced and that the battery needs to be replaced.

The battery itself actually isn't "smart" in the sense of smart devices we have these days. It will still require some other electronic device to actually read the copper layer's voltage. That layer can actually also be used to determine where exactly the dendrites will pierce. To some extent, the copper layer only gives a very immediate warning of impending doom, but the researchers claim that an even earlier warning sign can be had by placing the copper layer closer to the anode.

Such features will soon become a necessity as the number of devices using lithium-ion batteries grow around us. Aside from smartphones and laptops, these batteries are also used to power up plane systems, like the Boeing 787 whose battery packs caught fire in several incidents in 2013. Electric vehicles will also utilize this type of battery and in massive amounts, making early warning signs like these even more critical to saving lives as well as property.

SOURCE: Stanford