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Material has better properties than past sulfur-based batteries

University of Arizona (UA) biochemistry/chemistry professor Jeffrey Pyun and his doctoral student Jared Griebel have published an intriguing study, offering up a new sulfur-based polymer which transforms cheap, abundant waste sulfur -- the kind that's filtered out of burnt fossil fuel exhaust to prevent acid rain pollution -- into a polymer.

I. From Trash to Treasure

The new polymer can be used both structurally and in polymeric battery electrodes.

The new plastic is light and rugged.  The pair bill it as highly promising when paired with liquid lithium in battery cells.  The invention comes at an opportune time -- sulfur production is outpacing stock. At North America's largest oil refineries, such as Ft. McMurray in Alberta, refiners have taken to storing powder sulfur in dusty yellow "mountains" waiting for somebody to come up for a clever use for it.

According to Jered Griebel's calculations, 0.5 lb of sulfur is produced per every 19 gallons of refined gasoline.  While some of that waste is used to make sulfuric acid, much of it is piling up unused.  Professor Pyun bills the resource as the "garbage of transportation", adding [press release], "There's so much of it we don't know what to do with it."

Sulfur pile
Oil refiners are literally piling up "mountains" of unsold waste sulfur, waiting for an invention like this to come along. [Image Source: Ken Cooper Photography]

The pair has filed for a patent on their process.

The production of the new sulfur polymer begins with liquefying the sulfur at high temperatures and pressures (sulfur has a boiling point of roughly 441 degrees Celsius under standard temperatures) via inverse vulcanization.  The researchers had to hunt down special materials -- most don't like to blend with the molten sulfur.

II. First Time's the Charm

Ironically, the first material tried of 20 potential candidates worked out the best by far; the rest proved duds.  The resulting polymer is between 50 and 90 percent sulfur by weight.

The batteries made from the polymer have better capacity retention (how long charge is preserved) than past Li-S batteries.  They also have a higher specific capacity (823 mAh/g at 100 cycles) than past designs, meaning they could store more energy.  The relative stability of the Li-S sulfur polymer battery could make them an attractive target for automotive, aerospace, and personal electronics uses where traditional lithium ion batteries have suffered flammability issues.

sulfur polymer
A petri dish made from the new polymer, next to a pile of raw sulfur. [Image Source: UA]

In addition to the patent, the authors published an article [abstract] on the work in the prestigious peer-reviewed journal Nature Chemistry.  They had a lot of help -- other coauthors listed on the paper 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.

The research was funded by the UA, The National Research Foundation of Korea, the Korean Ministry of Education, Science and Technology, and the American Chemical Society.

Mr. Griebel has won an innovation award for his work.

Sources: Nature Chemistry [abstract], Eurekalert [press release], AZ Star



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RE: You can almost make anything from anything
By Mint on 4/15/2013 11:20:16 PM , Rating: 3
According to Nissan, the Leaf only needs 4kg of lithium (21 kg lithium carbonate) for its 24kWh battery, so if your figures are right, that's only ~$100 of raw material per car.

The cost of batteries is in the other materials (especially quality graphite, AFAIK) and the manufacturing process.

Lithium sulfur is definitely going to find its way into consumer electronics first. The lifetime requirements are lower and the price premium for high density is very high per Wh.


By mcnabney on 4/16/2013 1:37:50 PM , Rating: 2
That is interesting. I wonder why the industry goes on and on about the cost and availability of lithium as the limiting factor in batteries?


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