What does the future hold for battery technology?

The hard cell

09 July 2008 00:00  [Source: ICB]

Lithium ion batteries currently dominate the electronic device market. But how much more can they be developed - and will new technology make them obsolete?

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Louise Cole/Northallerton

DESPITE THE chill of economic slowdown spreading through the US and Europe, the electronic device market is still booming.

Its appeal is not just for consumers of the laptop or MP3 player generation, but for industry, where handheld devices are replacing clipboards and paperwork, and providing higher levels of accuracy in tests once performed by hand. The huge potential of electronic devices is driving the battery market - both rechargeable and disposable - to greater growth than ever before.

A report on the US battery market by Specialists in Business Information (SBI) published in May estimates that its value has risen by 2% from $7.9bn (€5bn) in 2006, to $8.1bn, with the primary and rechargeable battery market expected to grow, despite challenging economic times and a compound annual growth rate of 4% through to 2012.

CONVENTIONAL TECHNOLOGY

Basic battery technology has not changed much in the past century, but battery chemistries have become more refined. Modern products are driving a greater need for convenience - which often means wireless and rapidly rechargeable - longer cell life, higher energy density and complete safety and stability of the power source.

Lithium ion (Li-ion) batteries have become the most common form of rechargeable power source found in PCs, laptops and mobile phones because of their ability to pack energy into a small, light package.

In automotive applications, batteries must tolerate thermal extremes, vibration, driver abuse, environmental demands and a constant request for power and recharging. Electronic goods do not face any of these issues and yet some of the pros and cons of Li-ion batteries span the two markets.

"Lithium is the most reactive element and the lightest metal you can get, so there is not much more energy density to be had," says Barrie Lawson, business development director at UK battery manufacturer Axeon.

"But performance can be boosted in other ways. There are still limitations with lithium. If you recharge at low temperatures or if you recharge too quickly, you get plating on the anode."

If cells become too hot, the electrolytes begin to degrade. Sometimes this can cause a large energy release and oxidization, which can cause a fire - a process known as thermal runaway. Lithium titanate is a much safer and more stable option than the more usual lithium cobalt, for example, but the titanate gives only 2.5V against cobalt's 3.7V, so safety comes at a price. Equally, lithium iron phosphate - subject of many disputed patents - is safer but with a lower energy yield.

Li-ion batteries have improved on basic battery design in that the electrolyte is simply a transport mechanism. It is unaffected itself as the ions at anode and cathode penetrate the intercalation compounds at either end.

Lawson believes, however, that there are no holy grails to be found in battery development. Li-ion batteries will continue to perform well and become safer and more reliable. But he does not believe in radical departures. "It will be refinement of existing chemistry from now on," he says. "There are no new compounds that will give higher energy density."

Where does that leave fuel cells, microbial breakthroughs and nanotechnology? Lawson is a skeptic.

"In the trade, everyone has always said fuel cells are the power source of the future and they always will be. It's always another five years. I don't see them having any impact for a long time." He believes fuel cells are expensive and problematic. "Why not just carry a battery?" he asks.

THE FUEL CELL LOBBY

Fuel cells are expensive to develop and manufacture, although one advantage in the consumer goods market is that fuel cells operate better when they are small.

Methanol fuel cells have now been accepted by the US Transportation Department to allow the methanol cartridges that power fuel cells to be carried on flights. This is seen as a breakthrough for fuel cells manufactured by such companies as MTI Micro, which manufactures the Mobion direct methanol fuel cell technology (DMFC) that will power handheld devices. It is expected that Toshiba and other laptop manufacturers will bring the results of their DMFC research to the laptop market. The attraction to consumers is likely to be convenience rather than cost or sustainability.

DMFC technology is challenging. The methanol reacts with water the water is consumed at the anode and produced at the cathode and usually requires pumps to circulate it. Alternatively, the water and methanol are mixed in the same tank but this lowers energy output. Mobion avoids pumps by feeding pure methanol directly into the anode.

MTI has prototypes of DMFC additional power sources such as camera grips, which it says will pack twice the punch of a lithium source and an embedded source aimed at GPS and mobile phones which will recharge by hot-swapping methanol cartridges or an external power charger. This would plug into handhelds via a USB connection.

MTI is currently looking for a manufacturing partner, which may well be in China. It has three original equipment manufacturer deals, with South Korea's Samsung for mobile phones, a Japanese camera maker, and a military supply firm. Crucially, it also has a deal with US battery maker Duracell for the commercial production and supply of methanol cartridges through retailers.

HOLD IT IN RESERVE

Currently, several new cell designs have come out that offer reserve energy - a short blast of high-voltage energy that will allow data to be backed up in the event of a power failure. Their chief innovation is their ability to lie completely dormant without power drain until they are activated. Previously, only the thermal batteries used by the military had this guaranteed longevity of power.

US firm mPhase Technologies has been developing nanotechnology applications and microfluidics to improve battery performance. Its subsidiary, AlwaysReady, is developing its Smart NanoBattery - a reserve lithium battery designed for portable electronics. This uses a new way to separate the liquid electrolyte from the solid electrodes to keep the battery fully charged until the user "activates" the battery - allowing it to be stored for decades without losing energy.

"The Smart NanoBattery is the first reserve lithium battery with virtually infinite shelf life, with automatic, manual or remote activation, and with the size and functional versatility to meet the needs of the emerging portable electronics industry," says AlwaysReady CEO Fred Allen. He believes the company can build on the technology not only for backup power for a wide range of commercial, military and medical applications, but eventually as a primary power source.

"The rapidly emerging field of energy harvesting represents another arena of potential applications for the Smart NanoBattery," he says, referring to the fact that alternative power sources do not produce consistent energy and therefore need long-term backup supplies. He feels that giving users greater control of battery management is one step forward. Energy harvesting can also open up new avenues for recharging and sequential cells could be linked, with each retaining full charge until activated.

"We are seeking to revolutionize the battery industry by creating a new battery architecture, using existing chemistries, which allows more user control and numerous other distinct advantages, including higher energy density, longer shelf life, lower manufacturing cost and greater environmental friendliness." Sustainability concerns have driven AlwaysReady to design a battery that can be chemically neutralized before disposal.

But Allen says that although AlwaysReady will release its first commercial product within the year, developing truly new architectures amid emerging markets such as nanotechnology takes considerable funding and time, and this will continue to be a challenge for start-ups such as his.

Bio fuel cells are also in development. The UK-based Centre for Process Innovation has been working with Harvard University scientists in the US to develop its microbial LED light source, which can run on soil or other organic matter. Meanwhile, Japanese electronics giant Sony has developed a bio cell that runs on sugars. Four connected together gave enough energy to run a Sony Walkman, and of course carbohydrates are an easily renewable power source.

Discuss technological advances and their pros and cons





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