December 21, 2005 — Battery-powered toys, radios, and portable electronic devices make fun Christmas gifts - until the batteries run down. But advances in rechargeable thin-film lithium battery technology at Oak Ridge National Laboratory might one day provide a solution to the dead-battery dilemma.
Traditional alkaline batteries can be short-lived in some devices, costly over the life of the device and inconvenient to replace. Rechargeable batteries made from highly toxic heavy metals can pollute the environment. Others have a short storage life (a rapid "self-discharge" rate). If used improperly, some lose the ability to hold a full charge, a problem known as the "memory effect."
Nancy Dudney, group leader of the Ceramic Thin Films Group in ORNL's Condensed Matter Sciences Division said thin-film lithium batteries last longer; hold their charge better during storage; recharge faster with no memory effects; can be recharged many times and can be made much smaller, lighter and more flexible than traditional batteries. Also, since they are entirely solid and contain no liquids, potential problems and hazards due to leakage, corrosion, and freezing are eliminated.
"Rechargeable thin film lithium technologies offer several advantages over conventional batteries," Dudney said. "We are still a long way from seeing them used in everyday applications like toys and games. But they are an outstanding power source for highly specialized, critical purpose applications today and hold the potential for a wider range of application in the future."
Current applications for thin-film rechargeable lithium batteries include implantable medical devices, remote sensors, miniature transmitters, smart cards, and microelectronic devices, Dudney said.
Supported by the Department of Energy's Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, and Laboratory Technology Transfer Research Program, ORNL has developed materials for thin film lithium batteries that withstand temperatures from below zero to 250ÁC (480ÁF), Dudney said. This opens the door to different product designs, such as soldering the batteries into integrated circuits to power microelectronic devices. ORNL also working to make thin film lithium power sources smaller, lighter and more flexible, she said.
The drawbacks: thin film lithium batteries are more expensive than other small capacity batteries because they are more complex to manufacture and because they are still manufactured in much smaller numbers. They also are not available in standard cell sizes (AA, C and D).
But, while still years from replacing cheap alkaline batteries in toys, dolls, games, and other common Christmas gifts, the technology has other potential "holiday" applications, such as being used for radio frequency identification to track packages during the holiday shipping rush and "smart card" transactions during holiday spending.
Batteries for these and a variety of other applications are being developed by Oak Ridge Micro-Energy, Teledyne Electronic Technologies, Cymbet, Inc., Excellatron, Inc., Infinite Power Solutions and Front Edge Technologies. Each of these companies holds licenses for the ORNL technology.
John Bates, former head of the Ceramic Thin Films Group and Chief Technical Officer and founder of Oak Ridge Micro-Energy, a local thin film lithium battery technology firm, said companies are interested in the technology as backup power for computer memory chips and to power sensors embedded in tire sidewalls. These applications require the batteries to survive temperatures up to 280C during assembly which they can in the discharged state. There also is interest in using our batteries in small implantable medical devices for diagnosis, repair, and drug delivery.
Bates said progress is being made toward a lower-priced, mass-produced, thin-film lithium power source that is practical for a wider range of applications. In September, his firm announced a successful first manufacturing run of thin-film lithium and lithium-ion batteries with better than expected yields.
"As we continue to improve our pilot line and produce larger quantities, we will be able to deliver batteries into several small specialized markets. Our goal is to find a manufacturing partner who can produce 50 to 80 M batteries/year required for embedded tire sensors and non-volatile computer memory chips."