Apr. 14, 2013 — A new chemical process can transform waste sulfur into a lightweight plastic that may improve batteries for electric cars, reports a University of Arizona-led team. The new plastic has other potential uses, including optical uses.
Next-generation lithium-sulfur, or Li-S, batteries will be better for electric and hybrid cars and for military uses because they are more efficient, lighter and cheaper than those currently used, said Pyun, a UA associate professor of chemistry and biochemistry.
The new plastic has great promise as something that can be produced easily and inexpensively on an industrial scale, he said.
Although there are some industrial uses for sulfur, the amount generated from refining fossil fuels far outstrips the current need for the element. Some oil refineries, such as those in Ft. McMurray in Alberta, are accumulating yellow mountains of waste sulfur.
"There's so much of it we don't know what to do with it," said Pyun. He calls the left-over sulfur "the garbage of transportation."
Pyun and Griebel's co-authors are Woo Jin Chung, Adam G. Simmonds, Hyun Jun Ji, Philip T. Dirlam, Richard S. Glass and Árpád Somogyi of the UA; Eui Tae Kim, Hyunsik Yoon, Jungjin Park, Yung-Eun Sung, and Kookheon Char of Seoul National University in Korea; Jeong Jae Wie, Ngoc A. Nguyen, Brett W. Guralnick and Michael E. Mackay of the University of Delaware in Newark; and Patrick Theato of the University of Hamburg in Germany.
Pyun wanted to apply his expertise as a chemist to energy-related research. He knew about the world's glut of elemental sulfur at fossil fuel refineries -- so he focused on how chemistry could use the cheap sulfur to satisfy the need for good Li-S batteries.
Pyun and his colleagues identified the chemicals most likely to polymerize sulfur and girded themselves for the long process of testing those chemicals one by one by one. More than 20 chemicals were on the list.
They got lucky.
"The first one worked -- and nothing else thereafter," Pyun said.
They've dubbed their process "inverse vulcanization" because it requires mostly sulfur with a small amount of an additive. Vulcanization is the chemical process that makes rubber more durable by adding a small amount of sulfur to rubber.
The new plastic performs better in batteries than elemental sulfur, Pyun said, because batteries with cathodes made of elemental sulfur can be used and recharged only a limited number of times before they fail.
The new plastic has electrochemical properties superior to those of the elemental sulfur now used in Li-S batteries, the researchers report. The team's batteries exhibited high specific capacity (823 mAh/g at 100 cycles) and enhanced capacity retention.
- Woo Jin Chung, Jared J. Griebel, Eui Tae Kim, Hyunsik Yoon, Adam G. Simmonds, Hyun Jun Ji, Philip T. Dirlam, Richard S. Glass, Jeong Jae Wie, Ngoc A. Nguyen, Brett W. Guralnick, Jungjin Park, Árpád Somogyi, Patrick Theato, Michael E. Mackay, Yung-Eun Sung, Kookheon Char, Jeffrey Pyun. The use of elemental sulfur as an alternative feedstock for polymeric materials. Nature Chemistry, 2013; DOI: 10.1038/nchem.1624
Note: If no author is given, the source is cited instead.