The powerful lithium-based batteries used in electric vehicle systems, laptops and cell phones are prone to overheating and even blowing up, but adding less than a gram of a new substance could keep both temperatures and costs down, federal researchers say.

The molecule, developed by researchers Khalil Amine and Zonghai Chen at Argonne National Laboratory, is being tested as an additive in the electrolyte of lithium batteries to keep cell voltage from going too high.

The batteries used in hybrid and electric vehicles typically consist of 200 to 400 small cells, strung together into one powerful whole. Individual cells sometimes overcharge, emitting heat when they reach too high a voltage and pushing neighboring cells past the breaking point to set off a runaway thermal reaction.

Because electric and hybrid vehicles are constantly discharging and recharging during normal driving, overcharging problems are not confined to the garage but pose a real operational hazard.

In the lab, Amine and Chen discovered they could make a molecule based on boron and fluorine and add a tiny amount of it to each cell to control charging. When the cell exceeds the safe voltage level, Amine explained, the molecule picks up electrons and keeps the cell charge from going up.

Currently, expensive electronic controls are used to regulate each individual cell in a battery and shut it down if the voltage gets too high. But the control systems are expensive, making up as much as 20 percent of a battery's cost, and the electronics are prone to failing.

Amine said the new approach offers several advantages over current technologies. In addition to the lower cost, the molecule is more reliable, he said. Other systems that use some kind of molecule in a similar way cannot control more than one overheating cycle, he said, while his molecule will soak up extra voltage through 500 or more cycles.

The material is not easy to make, but only a small amount is needed -- 2 to 3 percent of the electrolyte by weight. Today, it costs about $1,000 per kilogram, but Amine said battery company EnerDel is leasing the technology and using an Energy Department grant to scale up the fabrication process. He believes that making large batches should bring the cost down to about $100 per kilogram.

The molecule could save $100 to $200 per battery, Amine said. Battery makers today are targeting a total price of $500 to $1,000 per battery.

One more advantage of the new molecule is that unlike the sophisticated electronic control systems, adding a new chemical to the battery pack is quick and easy. "The electrolyte is the last thing you fill in, so it's an immediate adaptation. Just add this 2 percent and you're ready to go," Amine said.

Reprinted from Greenwire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500

5 Comments

1. 1. Jokunen 08:47 PM 8/24/09

   Previously the excess recharging energy would be converted to heat and now it is converted to what? This sucker molecule just takes those extra electrons up?And what happens later when the cell is being discharged?

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2. 2. Lars Fischer 05:43 AM 8/25/09

   Uh, aren't you goint to tell us what this magic molecule actually is? There are people out here who actually do understand chemistry.

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3. 3. jerryd 03:14 PM 8/25/09

   Lars, this is SciAm, they don't bother with such details like facts sadly.
   
   Other detail is while some present packs are 200-400 cells, in the near future they will only be 20-100 cells as it saves much money, labor.
   
   While if it works as they say I don't see how it reduces costs as you still need the electronics to monitor and keep low voltage from damaging cells.
   
   Nor are electronics designed well prone to failure. Many TV sets last 20 yrs without problems and they are very inexpensively made. And it will have a monitor circuits to warn of battery problems anyway. And in mass production, electronics are cheap. I know as 30 yrs ago I had to give them up as they were to cheap to repair.
   
   And what are they calling a battery? The pack? A cell? Far too cheap mentioned for a pack and far too expensive for a cell.

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4. 4. Quinn the Eskimo 02:14 AM 8/29/09

   Who's going to power the Grid? Oh, and what grid is that, exactly?
   
   I'm just sayin'

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5. 5. thonycortes 02:33 AM 9/4/09

   As far as i can say that every year we develop a new product and maybe next year they could improve the laptop battery as well. Just like cars that every year has its own improvement.....

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