As the World of Li-ion Battery Safety Turns

December 19, 2006 by Jeff Shepard

For those in the lithium-ion (Li-ion) battery and portable electronics manufacturing industries who thought that the "year of the flaming battery" couldn't come to an end soon enough, more disconcerting news came out of Asia in December to remind them that, as some analysts have forewarned, Li-ion battery technology may be a "dead-end."

NTT DoCoMo Inc. and Mitsubishi Electric Corp. announced that the companies would have to replace 1.3 million batteries supplied by Sanyo Electric because they may catch fire and overheat. The batteries, manufactured by Sanyo GS Soft Energy Co., a 51% owned subsidiary of Sanyo, and GS Yuasa Corp. of Japan, contain deformed electrode plates, which can pierce the cell's internal insulation after a shock and cause an electrical short during charging. They were used in DoCoMo handsets. Sanyo, which was already in the midst of a three-year slump in terms of declining sales of its mobile phones and digital cameras, then witnessed its shares fall to a 31-year low – not a good sign for the world's largest manufacturer of rechargeable batteries.

Further troubling news came later in the month as battery safety concerns spread to the US auto aftermarket. The US Consumer Product Safety Commission and Clarion Corp. issued a joint announcement that batteries used in 2,500 Clarion N.I.C.E. P200 navigation units and entertainment systems were being voluntarily recalled due to potential overheating and fire hazard concerns. The Li-ion batteries were manufactured by Kiryung Electronics of South Korea.

Thus far, the discussions of remedies to the unstable Li-ion battery situation have centered on addressing the problem from an in-house manufacturing angle (i.e. eliminating the glitches during assembly that lead to metal particles being embedded in the batteries – Sony's initial rationalization of the problem). Hence, the attention being given to the efforts of the IEEE Standards Association to revise the existing IEEE 1625™, "IEEE Standard for Rechargeable Batteries for Portable Computing." The IEEE efforts are intended to "clean-up" the situation by devising a new safety standard by the end of 2007. Nonetheless, and perhaps due to the increasing realization that there isn't much more power that can be squeezed into a Li-ion battery (even as power consumption demands continue to increase), some companies are beginning to address the problem more from a design and technology angle.

Sony Corp. is investigating the potential of Lithium ion polymer (LiPo) batteries (used in model airplanes) as an alternative for its next laptop battery design. LiPo batteries are lighter than their metal-based Li-ion counterparts, since the lithium is held in a gel-like polymer. The LiPo batteries are said to be less flammable and to have an energy density that is about 20% better than Li-ion cells. LiPo batteries were used in Mitsubishi's unsuccessful Pedion notebook in 1997, but have since been successfully incorporated by Apple into its MacBook Pro notebook computers. Sanyo has also recently announced that it has developed a LiPo battery that is less than 4mm thin. Nonetheless, there have been some reports of LiPo battery fires.

Matsushita Electric Industrial Co., known globally for its Panasonic brand products, announced that it is now ready to mass-produce a new type of Li-ion battery, which is said to incorporate new technology to improve safety. The company began shipping what it claims is the industry's first 2.9Ah high-capacity batteries in April. The new technology is said to improve safety by forming a heat resistance layer (HRL) consisting of an insulating metal oxide on the surface of the electrodes. Lithium-ion batteries contain a thin polyolefin separator to insulate the cathode from the anode. When a separator is pierced by an electrically conductive material such as a metal particle, a short-circuit develops, causing the battery to overheat and, in the worst case, catch fire. The HRL used in the Panasonic battery, however, has better insulating and heat-resistant characteristics than polyolefin. According to the company, even if a short-circuit occurs, it will cease without causing the battery to overheat.

These developments occur at a time when the question of power capacity for portable products is intensifying. Laptop users who upgrade to Microsoft's Windows Vista™ are now being warned that they may have to disable some of the new operating system's advanced graphics features to avoid seeing a decrease in battery life in comparison to Windows XP. The drop is expected to result from the extra power needed to run the high-end processors, graphics cards and memory capacity required to support Vista. PC and hardware vendors may see Vista as a windfall because it requires faster and more powerful computers, but the extra power may come at a price. Specifically, since Vista demands more compute resources for an application than XP, users may have have to choose between a heavier battery, shorter battery life, or disabling some of the advanced Vista graphics.