SAN FRANCISCO, Calif.- New variations in the chemistry used for lithium ion batteries promise longer life for notebook computers. However, the changes will also force new trade offs in the power electronics of those systems.

Battery makers have had trouble squeezing significant performance gains out of the lithium ion cells over the last few years. Annual improvements in lithium ion capacity for notebooks has shrunk to three percent since 2005, down from seven percent a year previously, said Andy Keates, a battery program manager at Intel Corp.

The battery divisions of Samsung and Panasonic reported on separate efforts that could drive the gains to double-digit levels. However, some of the improvements depend on making vendor-specific changes in notebook charge and discharge voltages, Keates said.

 ”The traditional lithium ion cobalt chemistry is changing to achieve higher densities, but that comes at a price of new charge and discharge voltages and new parameters in capacity, cycle life and sustained power performance,” said Keates in a presentation at the Intel Developer Forum. “And those changes can differ by vendor,” he added.

For example, some battery makers are pushing charge levels to 4.35 volts and higher, while they are recommending notebooks continue to draw power from batteries down to levels of 2.5 and even 2 volts. That requires new voltage regulators and battery management policies.

“Battery makers want you to squeeze every ounce of energy out down to 2.5 or 2V levels, but you may not want to go all the way down,” Keates told notebook makers at a presentation at IDF.

Samsung SDI America (Irvine, Calif.) has a 3 Amp Hour lithium ion battery in production now that uses a cathode doped with aluminum and other materials, and employs an extra coating on its anode to speed electrolyte reactions. However, the battery only supports 300 charge cycles; a version that supports 1,000 charge cycles has a maximum density of 2.8Ah.

Samsung aims to ship in the fall of 2010 a battery that uses a silver-based anode to provide up to 30 percent greater energy density. It will charge at 4.35V and discharge down to 2.5V.

“We found 33 percent of consumers will spend $45 for an extra hour battery life,” said Sean Lee, a marketing director for the Samsung battery group.

Panasonic Corp. Energy Co. released a 2.9Ah battery in 2006 using nickel. It is now working on a 3.6Ah battery with a mixture of nickel and aluminum, said Atsuo Yoneda, a staff engineer in the group. It is aiming to use the extra density to create a smaller battery with the same density as today’s laptop batteries targeting thin and light notebooks.

 ”We’re just seeing the beginnings of these new chemistries, so it’s hard to predict” future performance gains,” said Intel’s Keates. “Lithium ion continues to be the best battery [for notebooks] in capacity,” he added.