Lithium-Ion Batteries to Survive Notebooks Flames

 
 
By John G. Spooner  |  Posted 2006-10-06
 
 
 

Lithium-Ion Batteries to Survive Notebooks Flames


Despite the recent recalls of millions of notebook battery packs, lithium-ion battery technology appears to be here to stay when it comes to powering portable PCs, experts say.

Following similar actions by Apple Computer, Dell, Lenovo Group, Toshiba and others— companies that have recalled more than 7.5 million notebook battery packs since Dells Aug. 14 recall of 4.1 million battery packs—Hitachi on Oct. 6 said it would recall 16,000 notebook battery packs.

The spate of recalls, which were all prompted by a manufacturing defect in Sony lithium-ion cells, highlights the potentially volatile nature of lithium-ion cells internal chemistry. Due to the defect, some cells could short circuit, produce large amounts of heat and ultimately catch fire, although only a relative handful have done so thus far.

In toto, manufacturers reported under 50 incidents. Dell, for example, counted only six total incidents in the United States, while Lenovo saw only one notebook fire before it issued its recall of 526,000 packs. Given that many tens of millions of battery packs shipped during the two-year time period covered by the recalls, most PC makers such as Dell and Hewlett-Packard insist that the technology is safe.

Moreover, although the recalls have sparked moves by some in the PC industry to increase the care with which lithium-ion cells are manufactured—one group is working to establish universal cell manufacturing standards, for example—there appear to be few lithium-ion alternatives on the horizon at the moment that dont involve trade-offs in energy density, cost or both.

Some options, such as zinc-silver batteries, use entirely different chemistries, while others reformulate lithium-ion designs by introducing new materials. Numerous manufacturers are also designing fuel cells, which convert hydrogen into electricity. But none are without challenges, ensuring that in the absence of a dark horse replacement candidate, lithium-ion or some version of the chemistry is likely to power notebooks for years to come.

What are PC makers doing to try to improve battery cell safety? Click here to read more.

"We dont see lithium-ion going away any time soon," said John Wozniak, a master technologist in the mobile group of Hewlett-Packards Personal Systems Group, in Houston.

Instead, "Were still going to see lithium-ion gain [in energy capacity] for a while and its still going to be the main player" for notebooks, Wozniak said. Manufacturers "are all swizzling the mix as we speak to get that next incremental gain."

Lithium-ion battery cells tend to see about an 8-10 percent gain per year in energy capacity, yielding battery packs with higher watt-hours, a figure that shows how much time a given pack, usually made up of six individual cells, can sustain an output of a specific number of watts.

Right now, most notebooks come with 50-55 watt-hour battery packs, which are good for around 4 hours of run-time per charge on a standard notebook, which consumes around 13 watts on average. Some initiatives, such as Intels Extended Battery Life Working Groups "8-in-08" effort, which seeks to help standard notebooks reach 8 hours of run-time per battery charge in 2008, are pushing for more battery power, or working to curb notebooks appetites for watts.

To get to 8 hours on a single charge of a six-cell pack, notebook battery energy capacity must rise to 72 watt hours or more by 2008, while notebook average power consumption must fall to about 9 watts. Intel is confident that both will happen in 2008, the company has said.

Meanwhile, "These [potential replacement] technologies have been around for a while, but theyve always been pie-in-the-sky type ideas just because battery technology moves so slowly," said Richard Shim, an analyst at IDC, in San Mateo, Calif.

"There are certain things [cell makers] can still do with lithium-ion that will make it safer," Shim said. "I think theres still room for this technology to improve. Its just that that there hasnt been as much emphasis [on improving lithium-ion technology] in the past, because the recalls havent been on this scale."

Still, Shim said the Sony cell battery pack recalls were not evidence of a fundamental problem with the lithium-ion approach itself, despite its chemistry, which requires volatile hydrocarbons to be used in the electrolyte solution of each battery cell. Manufacturing defects and not design flaws led to fires in a handful of Dell machines and the single Lenovo ThinkPad, he emphasized.

What is Dell doing to help customers with its battery recall? Click here to read more.

Even those who market alternatives for lithium-ion batteries say they feel the technology will rule the roost for the foreseeable future. But they may challenge its market dominance all the same.

"The portable electronics industry has designed [products] around lithium-ion. Thats the only alternative theyve got right now unless they want to step back in terms of performance. We dont see that happening," said Ross Dueber, CEO of Zinc Matrix Power, in Camarillo, Calif.

However, he said, Zinc Matrix Power believes it has a potential successor to lithium-ion. The company, a startup backed by investors that include Intels Intel Capital arm, has demonstrated a 75 watt-hour battery pack, which is theoretically capable of running a standard business notebook for about 6 hours. The company will begin sampling battery packs that use its silver-zinc cells to PC makers in early 2007. It plans to begin wider production at mid-year, Dueber said.

"We think silver-zinc, our technology, is that next revolution in battery technology. But its going to take time to get the industry to evaluate it and adopt it," Dueber said. "Its not going to be an overnight event. It certainly is going to be a migration, so to speak."

Zinc Matrix Powers silver-zinc technology utilizes a silver electrode and a zinc cathode. The electrolyte itself is a water-based alkaline, similar to that of NiCd or NiMH (nickel-metal hydride) batteries. Lithium-ion replaced NiMH batteries over a period of years. NiMH batteries were still used in low-end notebooks until recently.

Zinc Matrix Power sees a similar transition period should its technology catch on with PC makers. Meanwhile, it will highlight what it says is the inherent safety of its technology.

"We all know what can happen with lithium-ion if [a cell] goes bad," Dueber said.

The companys silver-zinc batteries use "water as the basic working fluid. We know that water is not flammable. So the cells still vent [during an overheating situation], but all they do is spray out their alkaline-based water electrolyte. In this case you dont have the fire hazard you do with lithium-ion," Dueber said.

Lithium-ion cells look something like a soup can on the outside, while inside is a construction that looks like a jelly roll. Two strips of coated metal foil are separated by an insulating layer and wound up in a coil. The coil is placed in a metal can, filled with an electrolyte solution, and sealed. Silver-zinc cells would use the same basic construction, but with different materials. Lithium-ion batteries electrolyte solution is based on a mixture of ethylene carbonate or diethyl carbonate, Dueber said, making it possible for them to catch fire if a short causes an overheating situation.

"Cells can potentially fail if they get very hot due to external heating or excessive current flow, if they are overcharged, or if a short-circuit occurs between layers of the coil. This last problem was what led to the [Dell] recall: metal particles, contamination from the manufacturing process, are in very rare cases causing a short-circuit in the cell that leads to a fire," Forrest Norrod, Dells vice president of engineering, wrote in an Aug. 22 posting in Dells Direct2Dell blog.

However, silver-zinc faces challenges of its own, not the least of which is a lower working voltage of 1.5 volts versus lithium-ions roughly 3.6 volts. Lower battery cell voltages generally mean lower battery pack watt-hour potential, although Dueber said silver-zinc batteries make up for lower voltage with greater energy-density potential by volume than lithium-ion batteries have. The company also uses so-called prismatic cells, which are square-shaped (as compared with the cylindrical shape of a lithium-ion cell) and thus use more space for energy storage capacity inside a battery pack.

Even with as many orders as it could fill with the assistance of its manufacturing partner, Tyco Electronics, Zinc Matrix Power couldnt serve the entire notebook market, Dueber said.

Thus, ultimately, "We want to work with the manufacturers in order to bring silver-zinc technology to the marketplace. Certainly Sony, Sanyo and Panasonic are much larger. But weve got a good [intellectual property] position" and would license the technology to other players, he said. "The key for us is to get the technology out there in the hands of people [so they can] evaluate it, get them comfortable with it and then be able to call upon the infrastructure that already exists … in terms of manufacturing."

Next Page: Fuel cells offer different advantages and disadvantages.

Fuel Cells Offer Different


Advantages, Disadvantages">

Meanwhile, fuel cells also present an alternative source of power for notebook PCs. Numerous manufacturers are currently working on creating fuel cells that can be used with notebooks.

The first fuel cells, which are hitting the market now in small quantities from companies such as UltraCell, will be used as external power sources, becoming a portable electric outlet of sorts, for notebooks used by military units or scientists who currently have to carry numerous battery packs, said Ted Prescop, senior applications engineer at UltraCell, in Livermore, Calif.

"The main benefit to a fuel cell is you can get a lot more energy per pound than you can with a battery," Prescop said. "What a lot of fuel cell companies are struggling with is how to make a small system thats also affordable. Its going to take a few years … to get down in price to where average laptop users are going to consider [a fuel cell] as an alternative to batteries."

UltraCells first fuel cell, a 2.2-pound unit that costs about $1,000 and uses 1-liter methanol fuel cartridges, is sampling to some clients now and is scheduled to go into wider production in early 2007. The unit will serve as a universal power supply for several different notebook brands, he said.

Right now, "Fuel cells dont make sense for short run-times. It only makes sense if youre going to be running for a couple of days," he said. "Its much easier to bring along extra fuel than extra batteries."

Over time, fuel cells and fuel cartridges will come down in price and size, Prescop predicted, making them more consumer-friendly.

UltraCells second-generation fuel cell, which he said is being developed in the companys labs now, will be attachable to the back of a notebook and will work in concert with a notebooks battery. The cells half-liter fuel cartridge may stick out slightly, he said, but isnt likely to be more obtrusive than one of todays extended run-time battery packs. Travelers using the product could leave their AC adapters behind.

A third-generation integrated fuel cell, which could be built into a notebooks chassis, should arrive within about five years, Prescop said.

But even with a fuel cell present, a notebook is still likely to use a battery, given that fuel cells tend to deliver a constant rate of power, while notebooks needs vary. The companion battery, which is likely to be smaller than those used today, would also provide energy to start the fuel cell. However, its main purpose would be to act as a gas tank of sorts, storing energy from the fuel cell and then supplying it to the notebook according to the machines needs.

Theoretically, a small fuel cell with a 200-cubic-centimeter cartridge could meet most peoples needs, Prescop said. A fuel cell that provided 180 watt-hours of power per 200cc cartridge would supply enough juice to run a 10-watt ultraportable notebook for about 18 hours, for example.

But, despite the advances that are possible for fuel cells or the more immediate potential for silver-zincs ability to exceed the energy density of todays lithium-ion batteries, any potential replacement technology will still face a difficult road.

Given that PC makers such as HP operate on thin margins, costs—ranging from the costs involved in redesigning battery circuitry to the potential price premiums of new battery packs themselves—are all critical considerations.

"From a competitive standpoint, from a dollars-per-watt-hour perspective, will [zinc-silver] ever approach where lithium-ion is?" Wozniak asked.

For now, PC makers such as HP are likely to prefer to simply continue working to improve the safety and energy capacity of lithium-ion technology, he indicated.

Efforts are already afoot to do both.

Sanyo, Sony and Panasonic (of Matsushita Electrical Industrial Co.), the worlds top battery makers, continue to work to squeeze more out of lithium-ion technology. Intel and Panasonic, for example, have been collaborating to develop new lithium-ion cell designs that use nickel to increase their energy density. (An Intel representative said on Oct. 4 that company officials were unavailable to comment on the technology, while Panasonic officials in New Jersey did not return a call requesting more information on the battery technology.)

Companies are also exploring other approaches to lithium-ion technology, including one called lithium-ion phosphate. Valence Technology, of Austin, Texas, one company that is developing a lithium-ion phosphate technology, has said the approach is safer because its technology uses different types of materials, including a phosphate-based cathode, which are not prone to thermal runaway or overheating and will not burn.

However, none of the advances are without trade-offs, Wozniak said.

"Lithium-ion phosphate has been around a while and it is a safer chemistry for no other reason than [that] its a lower-energy chemistry," he said. At about 1.6 amp-hours, versus the 2.6 to 2.9 amp-hour ratings of current and near-future lithium-ion battery cells, "You need a battery thats half again as big to get the same amount of power. Its not well-suited for portable applications, really."

Thus, PC makers have begun working on ways to improve the safety of lithium-ion batteries by addressing the way the cells are made. The OEM Critical Components Committee of the electronics products standards body IPC recently met to begin work on a set of standards for manufacturing and testing lithium-ion cells. Its aim is to raise the bar for battery cell makers and therefore make it less likely for contaminants to enter the cells during manufacturing.

Others are doing work individually. HP has been working with a company called Boston-Power, Wozniak said.

He said Boston-Power is formulating a revised lithium-ion battery chemistry that can lengthen battery packs life cycles by roughly tripling the number of charge/discharge cycles they can endure before their ability to store energy degrades.

However, ultimately, "You cant sell safety," he said. "You cant say, Heres my regular battery and heres my safer one. If you come up with a technology thats safer, it has to be licensed across the industry to have an impact."

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