Lithium-Sulfur Battery X-Rayed

Category: Science & Technology
Posted: July 18, 2012 01:59PM
Author: Guest_Jim_*

Right now I have at least ten lithium-ion batteries within arm's reach. The reason this kind of battery is used as much as it is has to do with its relatively high energy density and its ability to be recharged multiple times without failing. Unfortunately these batteries are not cheap, especially when considering larger batteries like those in electric vehicles which can represent more than half of the vehicle's total cost. A potential replacement is the lithium-sulfur battery which can store five times more energy while being cheaper, but it has one major flaw.

Lithium-sulfur batteries can only be cycled 20 times or so before they completely fail. Researchers have been trying to understand why this happens, so they can prevent it. Previous studies have shown that the sulfur completely vanishes from the cathode, which makes the battery inoperable. However a new study from Stanford University and the SLAC National Accelerator Laboratory has found this is not completely true. The previous studies of the batteries used electron microscopes to examine the batteries after being cycled, disassembled, and cleaned. The Stanford researchers however used an X-ray microscope to peer into a battery while it operated and found the sulfur does not leave the cathode.

So why did the previous studies report the sulfur went missing and why don't the batteries last long? The researchers suggest the washing of the battery's components before being put under the electron microscope washed away whatever sulfur was there. The reason the batteries stop functioning though is because some sulfur will occasionally leave the cathode and bond, permanently, with the lithium. It does not take many of these lithium-sulfur crystals to prevent the battery from working. Now that researchers actually known what is happening, they can focus on fixing it.