Just how should you react to Dell Computer’s and Apple Computer’s recent recalls of nearly 6 million lithium-ion laptop batteries suspected of posing a fire hazard?
A selfish reaction always works for me. “Is my personal computer going to go up in flames?” And that question, at least, is easily satisfied with a visit to each manufacturer’s recall pages.
Dell, which recalled 4.1 million batteries last week, has set up a battery recall page that details all the models affected by the recall. A link at the bottom of the page will take you to photos of the affected batteries. Apple, which recalled another 1.8 million units yesterday, has likewise set up its own page with a list and photos of the affected models.
More information about voluntary recalls can be found in the U.S. Consumer Product Safety Commission’s pages on the Dell and Apple recalls. It turns out Dell received six complaints of overheating in batteries, while Apple has received nine overheating complaints, including two that resulted in minor burns. Sony Energy Corp. manufactured all of the batteries and estimates that the cost of the two battery recalls will amount to 20 to 30 million yen.
Fortunately, no truly serious injuries have been reported. But this latest battery blowup raises serious questions about the potential hazards and utility of lithium-ion batteries. Most of the blame lies with the commonly used cathode materials - such as lithium cobalt - that have relatively poor thermal stability. In the worst cases, short circuits in the battery electronics, overcharge conditions, or even manufacturing defects in the battery cells can result in a nasty exothermic reaction known as thermal runaway.
In a press release issued after the Apple recall, Sony blames the overheating onmicroscopic metal particles in the recalled battery cells. These particles may come into contact with other parts of the battery cell, leading to a short circuit within the cell. “Typically, a battery pack will simply power off when a cell short circuit occurs. However, under certain rare conditions, an internal short circuit may lead to cell overheating and potentially flames,” Sony states.
Though the biggest recall of its type, Dell and Apple are by no means alone in their recent battery woes. A long list of CPSC battery recalls since 1997 can be found on Valence Technology’s website. The company also offers battery safety white papers and technical presentations on different pages within the same site. And check out the video for a detailed explanation of why lithium-ion batteries can spontaneously combust.
Valence developed and recently patented an alternative to conventional lithium-ion batteries. Called Saphion, this battery technology relies on lithium-phosphate cathodes rather than the more popular - though less thermally stable - lithium cobalt. “Lithium-phosphate by its nature has a much higher thermal stability,” says Jim Akridge, Valence’s CEO, who explains that the energy contained in the battery is insufficient to break down phosphate and release oxygen.
Other alternative lithium-ion technologies are available too. A123 Systems has used nanoscale electrode materials to improve overall battery performance and safety. From a safety standpoint, the company claims these nanoscale electrode materials do not release oxygen at higher temperatures, thus heading off the risk of thermal runaway. Altair Nanotechnologies Inc. likewise developed nanoscale materials, including Li4Ti5O12, for use as battery electrodes.
Finally, if you’d like to brush up on battery technology, it may be time to go back to school - sort of. Battery University is an online guide to battery basics - including some charging strategies. It also contains links to a free, 300-page online book about battery technology called “Batteries In A Portable World.” It’s written by Isidor Buchmann, founder of Cadex Electronics, a specialist in battery analysis systems. Though he pitches the book as a guide for non-engineers, it nonetheless contains more than its share of technical data on the various battery chemistries in use today.