Apr. 30, 2002 UPTON, NY — Using nanoscale materials, researchers from the U.S. Department of Energy’s Brookhaven National Laboratory have developed a method to make electrodes that are suitable for use in rechargeable lithium ion batteries and other electronic devices. Because so many new and different materials can be made with this versatile method, it should be capable of producing electrodes that are more efficient and durable than those in use today.
Among the advantages of the new method as it applies to lithium ion batteries are that lithium alloys can be produced ex situ rather than by an initial activation process inside the battery. This makes the battery production process simpler and less time-consuming. Most importantly, the method allows great flexibility in choice of materials and makes possible the production of novel alloy compositions.
“Since unique alloys can be created using this method, the opportunity exists for making new types of electrodes with superior properties,” Brookhaven’s James Reilly, the principal researcher on the project, said. “Also, the method could likely be used in a number of other applications, including the preparation of nanocomposite catalysts.”
To make a lithium tin electrode, for example, the researchers mixed excess lithium hydride with tin oxide. Part of the lithium hydride reacts to form lithium oxide while the remainder reacts to form a lithium tin alloy. Hydrogen is removed as a gas. After the initial formation of the lithium tin alloy and lithium oxide composite, hydrogen is alternately added and removed. This treatment results in the formation of a nanocomposite material made of tiny grains with a diameter of 20-30 nanometers (one nanometer is a billionth of a meter). This small grain size makes the electrochemical reaction go faster because there is more surface area upon which the reaction can take place. The lithium oxide acts as inert support for the electrochemically active lithium tin alloy.
The researchers also mixed lithium aluminum hydride with tin oxide, and lithium aluminum hydride with silicon oxide to make similar nanocomposite electrodes. Reilly maintains that any one of the many elements that form stable metal hydrides could be used to make nanocomposite materials with the method created by his Brookhaven team.
Hydrogen is the key to forming nanocomposite materials in this new method. The hydrogen atoms are successively absorbed and desorbed from the lithium-tin alloy many times until it is broken down into tiny alloy grains. This chemical means of making nanocomposites is much more effective and practical than physically grinding materials to produce fine particles.
This research was funded by Office of Chemical Sciences of the U.S. Department of Energy. A patent is pending for this new method, and it is available for licensing by industry.
The U.S. Department of Energy’s Brookhaven National Laboratory (http://www.bnl.gov) conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies. Brookhaven also builds and operates major facilities available to university, industrial, and government scientists. The Laboratory is managed by Brookhaven Science Associates, a limited liability company founded by Stony Brook University and Battelle, a nonprofit applied science and technology organization.
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