Dell and Sony knew about and discussed manufacturing problems with Sony-made Lithium-Ion batteries as long as ten months ago, but held off on issuing a recall until those flaws were clearly linked to catastrophic failures causing those batteries to catch fire, a Sony Electronics spokesman said Friday.
Spokesman Rick Clancy said the companies had conversations in October 2005 and again in February 2006. Discussions were about the problem of small metal particles that had contaminated Lithium-Ion battery cells manufactured by Sony, causing batteries to fail and, in some cases, overheat.
As a result of those conversations, Sony made changes to its manufacturing process to minimize the presence and size of the particles in its batteries. However, the company did not recall batteries that it thought might contain the particles because it wasn't clear that they were dangerous, Clancy said.
"We didn't have confirmation of incidents [involving fires] until relatively recently. We received reports, but didn't know if there were environmental situations not related to the systems themselves," he said. "Different measures were taken in February and in October  to further ensure that there were as few of these particles as possible and that they were as small as possible."
On Tuesday, Dell and the U.S. Consumer Product Safety Commission (CPSC) announced they would recall 4.1 million Dell laptop battery packs, citing a fire hazard. The recall covers Dell-branded battery packs that use certain Sony Li-ion battery cells sold through July, 2006. Those batteries were manufactured prior to changes made in February, Clancy said.
Dell spokeswoman Anne Camden declined to comment on the conversations with Sony in October and February, but told InfoWorld that Dell was "confident that the manufacturing process at Sony has been changed to address this issue. Now our focus is erring on the side of caution to ensure no more incidents occur."
Lithium-Ion batteries are constructed with coated anode and cathode foils separated by thin layers of polymer material, said Dan Doughty, manager of the Advanced Power Sources Research and Development Department at Sandia National Laboratory.
"It looks like a jelly roll. You get a high surface area with thin layers. The thinner they go with the separators, the more room there is for the active material," Doughty said.
The coated layers are wound up on commercial machines to create the individual Li-ion cell, and it's at that stage that contaminants, such as metallic particals, can get embedded in the battery cell. The metallic particles mentioned by Sony and Dell may have been cast off by those commercial machines, he said.
Generally, the polymer separator is very thin -- less than 25 micron (one millionth of a meter) thick. If that is punctured by an electrically conductive material, like a metal particle, the battery cell's anode and cathode short circuit, Doughty said.
He said an internal short circuit was "the worst scenario in battery design, because there's nothing you can do to control it," he said. In contrast, manufacturers have a variety of measures to guard the battery contents from external threats, like ambient heat.