Tuesday, May 27, 2014
What happens inside a battery?
By: John Platt
Have you ever wondered what happens inside a battery? You're not alone; scientists are still searching for new clues to the processes that take place inside batteries as part of the ongoing quest to create better, more powerful, longer-lasting and cheaper energy-storage solutions.
A team of researchers with the Department of Energy's Pacific Northwest National Laboratory (PNNL) and other institutions have just unlocked some of the secrets hidden within rechargeable batteries. The work, published last month in the journal Nano Letters, could eventually lead to better rechargeable batteries, something that would help to further enable electric vehicles and alternative energies such as wind and solar.
Most research into batteries today focuses on studying "the hard-to-find solid electrolyte interphase layer, a coating that accumulates on the electrode's surface and dramatically influences battery performance," according to a recent news release from PNNL. Other research has been limited, however, because most high-powered microscope work is done under dry conditions. Most batteries, however, contain liquids, and until now, the liquids have slowed the ability to conduct microscopic research.
The team has come up with a new method that bathes battery electrodes in wet electrolytes, allowing them to view the activity in those electrodes under a high-powered microscope. PNNL materials scientist Chongmin Wang said in the press release that this new technique "will help us find the solid electrolyte layer" and that it helped to provide new information about electrode behavior. Specifically, it allowed them to study how positively charged ions ebb and flow into electrodes — and in the process deform them.
It's the latter part of the process that's the most important. As electrodes swell, they also break down. The more they break down, the less they will able to hold charges.
The researchers created a special dry battery for their tests. The battery — which was far smaller than the size of a dime — contained one silicon electrode and one lithium metal electrode within a bath of electrolyte, which was enough to allow the flow of ions but still allow study under a high-powered microscope. That allowed the team to study the electrodes' behavior and show that the dry battery behaved the same way as a wet battery.
"We have been studying battery materials with the dry, open cell for the last five years," Wang said in the press release. "We are glad to discover that the open cell provides accurate information with respect to how electrodes behave chemically. It is much easier to do, so we will continue to use them."
The researchers say this could new study could be the next step in the ongoing quest to create longer-lasting rechargeable batteries.