Aside from capacity, the worst thing about batteries is that they degrade with time, holding less power with every charge. But now scientists have developed a lithium ion material that can endure 30 times as many charge cycles as current cells.
Part of a collaboration between Sharp and Kyoto University, the new material—made of a lithium iron phosphate compound—is used at the cathode to increase the longevity of batteries. These days, a typical laptop battery can endure 300 cycles before it retains just 80 percent of its original charge; the new material will produce cells that hold 80 percent after a staggering 10,000 cycles.
The researchers knew that lithium iron phosphate held promise for use in batteries, but figured that they could make it incredibly durable by adding extra solute elements into the mix. But instead of doing that by hand and testing each and every possibility, they used computer simulations to model how extra elements would change the material's properties.
While there's no way to directly predict the lifespan of a battery made from these materials using computation, it is possible to estimate how their volumes change when they're lithiated and delithiated—that's fancy talk for charged and uncharged. It's those changes in volume that cause batteries to, quite physically, break down and reduce performance, as microcracks form in the structures.
The modeling found a theoretical new material with added silicon or aluminum would expand and contract by just three percent compared with a typical 6.5 percent for most current batteries. After synthesizing and testing the material in the lab, the researchers found that cells made using the material hold 80 percent of their charge after 10,000 cycles, and an amazing 70 percent after 25,000 cycles.
There's one small catch, though: the introduction of those extra elements means the initial capacity of the battery would be lower than usual in production units. Still, for some applications that might just be a cross worth bearing. [Nature Communications via Neomatica]
Image by Argonne National Labs / Creative Commons, Isao Tanaka