Scientists from NIST, the Univ. of Arizona in Tucson and Seoul National Univ. in Korea have combined common ingredients to make an inexpensive, high-capacity lithium-sulfur battery that can be cycled hundreds of times without losing function.
But sulfur cathodes have two major weaknesses. Sulfur easily combines with lithium to form compounds that crystallize and gum up the battery’s insides, and it tends to crack under the stress of repeated cycling. As a result, a typical lithium-sulfur battery becomes useless within a few dozen cycles—far too few for a laptop or car battery that may get cycled once a day for years.
To create a more stable cathode, the research team heated sulfur to 185 C, melting the element’s eight-atom rings into long chains. They then mixed the sulfur chains with DIB, a carbon-based plastic precursor that links the sulfur chains together, creating what is known as a co-polymer.
The researchers ran their optimized battery through 500 cycles and found that it retained more than half its initial capacity. Other experimental lithium-sulfur batteries have performed similarly, but their cathodes require more complex manufacturing processes that would be expensive to scale up