Graphene cuts battery recharge times

Batteries with Vorbeck's graphene material could reach devices next year

Smartphones or laptops could recharge in a matter of minutes if lithium-ion batteries are equipped with special graphene material from Vorbeck.

Vorbeck, a materials company, is working with U.S. Department of Energy's Pacific Northwest National Laboratory to implement its graphene material in batteries that could store large amounts of energy and recharge quickly, said John Lettow, president of Vorbeck.

Standard cell phone lithium-ion batteries might take two hours to recharge, but graphene can help batteries recharge in less than 10 minutes, Lettow said. The advance could help maintain energy storage capacities for longer periods while making batteries safer by preventing excessive heating.

"There are many problems with battery materials at present: they take a long time to charge and discharge, they do not store much energy, they have lower than desired cycle life, and they can heat up and short circuit, causing safety problems," Lettow said.

The technology has been tested in batteries in the lab, Lettow said. The nanomaterial could reach batteries for use in cell phones, laptops and power tools starting next year, he said. The material is being evaluated by battery companies for implementation in products.

Lithium-ion batteries typically recharge by transferring lithium ions between electrodes -- or the cathode and the anode. The rate at which current batteries are charged is limited by the electrode materials, Lettow said. Batteries today take a long time to charge because of the low electrical conductivity and lithium transport of the electrodes, which limits the lithium-ion exchange.

Vorbeck is looking to combine hybrid material that include graphene sheets coated with a thin layer of ion-storage material, so ion-storage and electron-conducting components are close. This allows electrons and lithium ions to combine much more quickly in the electrode, which allows for fast battery recharge times.

Graphene is chemically stable and has high electrical conductivity so it can move electrons easily. Improved cathodes and anodes also allow for storage of more lithium ions, which can increase the battery's capacity and give laptops longer battery life. 

Batteries with graphene can also last significantly longer than conventional batteries, Lettow said. Vorbeck's hybrid ion-storage materials can swell and flex without mechanical breakdown, which gives them a significantly longer cycle life in a battery, in some cases up to ten times longer, Lettow said. By comparison, as lithium ions are inserted and removed from electrode material in a typical battery, the material swells and shrinks, leading to a quick breakdown. 

The efficient conductivity of graphene also leads to less resistive heating within the electrode, so batteries can operate at lower temperatures, which adds to the battery safety, Lettow said. Lithium ions pile up in present battery materials too quickly, waiting to get in the electrode material. This creates an over-voltage situation that can result in overheating, and short circuits that have caused fires in several types of lithium-ion batteries, Lettow said. Because of this, battery manufacturers purposely limit the rate of charge and discharge to very low levels to keep the batteries in a stable operating regime. 

Vorbeck's Vor-x graphene material was developed based on technology licensed from Princeton University. The company has already used the material in applications like printing.

There is increasing focus on battery research. The research arm of IBM last year said it was working on high-density batteries for use in electric cars. The U.S. government in November assigned US$18 million to national laboratories for research on topics including safe batteries and battery development.

Copyright © 2010 IDG Communications, Inc.

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