Originally Published May 2000

INDUSTRY NEWS

Next-Generation Lithium-Ion Polymer Batteries Offer Improved Run Times, Increased Safety

New developments in lithium-based batteries have the potential to revolutionize the portable medical device industry. Lithium-ion (Li-ion) polymer batteries promise to vastly increase the run times of devices, are rechargeable, and weigh less and take up a smaller amount of space than conventional Ni-Cad and nickel-hydride batteries.

In addition, Li-ion polymer batteries, unlike standard Li-ion batteries, can be molded into any shape necessary since they use a gelatinous electrolyte in place of a liquid. Consequently there is no danger of leakage, the primary reason that traditional Li-ion batteries are flammable and prone to sparks. Finally, Li-ion batteries do not contain toxic heavy metals.

Lithium-ion polymer batteries such as the PowerPad 160 from Electro Fuel (Toronto) offer increased run times in a smaller package.

A number of companies have been working on these developments. Among these is Electrofuel (Toronto), which unveiled its Powerpad 160 Li-ion polymer battery in 1999. It offers an energy density of 470 W/L (183 Wh/kg), considerably higher than the 200–250 W/L common for conventional batteries. According to vice president of marketing David Murdoch, this marks the "biggest jump in energy density in the history of batteries."

The Powerpad 160 also has other advantages in comparison to standard batteries, Murdoch adds. First, it can function for 20,000 cycles (one cycle consists of a charge and discharge). Second, the battery's high density can help eliminate bulk.

Batteries achieve 16-hour run time in tests

Murdoch mentions that the battery powered an IBM 600-MHz laptop computer for 16 hours in tests, compared to the 2 hours of run time typical of conventional batteries. He indicated that hospitals have expressed interest in using the batteries with notebook computers used in bed-to-bed applications.

The company is interested in using the batteries in pacemakers, but is not focusing on medical possibilities in the near term because of obstacles in scale-up to mass production.

The Powerpad 160 comes in a standard A4 footprint and weighs 2.2 lb. Electrofuel is expecting to release a battery with an energy density of 225 Wh/kg (600 Wh/L) in 2001.

One company not experiencing difficulty in producing large quantities of batteries is Valence Technology (Henderson, NV). The company has been shipping its manganese Li-ion polymer batteries to customers for more than a year from its factory in Northern Ireland, which has the capacity to produce up to 15 million batteries a year.

Bill Battison, vice president of marketing for Valence, touts size flexibility as a main selling point. The company offers five sizes, including one that measures 8 x 12 in., and can also build the batteries to custom specifications.

An earlier problem involving low cycle life has been solved, according to Battison. The batteries now offer more than 1000 cycles at room temperature. The 4 x 4-in. battery has an energy density of 157 Wh/kg; the largest battery can provide 4.6 A/h of power.

Valence is focusing on applications with large footprints, including defibrillators and portable noninvasive medical devices, as well as cell phones and notebooks.

Illion Technology Corp. (Plymouth Meeting, PA), a product of a recent merger between Lithium Technology Corp. and Pacific Lithium Ltd. (Auckland, NZ), is planning to offer a Li-ion polymer battery based on Lithium Technology's proprietary fiber-web substrate technology.

The company will construct its batteries using Pacific Lithium's high-performance fibers and composite battery structures using continuous-flow fiber-web coating and handling methods. The company is ready to begin "large production [of the batteries] on a joint-venture basis," according to David Cade, chairman and chief executive officer of Illion Technology.

Toshiba America Electronics Inc. (Irvine, CA) recently began offering its Advanced Lithium Battery. Because it is devoid of liquid, the company plans to eliminate protection circuitry in this product by the end of this year. This should lower the cost and space required for the battery pack, giving "customers additional space to use a larger cell," says Ritch Russ.

Companies are taking different approaches

Toshiba America Electronics projects production to increase to 1 million cells a month by April, up from 500,000 cells in January.

Moltech Corp. (Tuscon, AZ) has taken a different approach through its development of a high-performance lithium-sulfur (Li-S) battery. Its technique creates a kind of 100-µm thin-film sandwich out of lithium and sulfur, which allows for a much lighter and thinner battery cell, according to David Williams, director of sales and marketing.

The company plans to offer the battery by the end of this year. The cells will have a voltage rating of 2.1 V per cell and an energy density of 200 Wh/kg (260–300 Wh/L), and will measure only a few millimeters thick, said Williams.

Also taking a different tack is Saft America (San Diego). It is offering what is described as the first medium prismatic batteries, according to product manager Andy Bartocci. Bartocci claims that the MP-series batteries provide the highest capacity on the market in a single cell, and that they can replace several cylindrical cells in a parallel arrangement.

The three versions of the batteries offer 1.8 Ah, 3.9 Ah, and 5.5 Ah, compared with 1.5–1.6 Ah for a conventional Li-ion battery. Using four MP 174865 batteries (with 3.9 Ah each) in a laptop computer allowed for 4 hours of run time.

Initial plans for the batteries include use in cell phones, laptop computers, and related equipment. Bartocci adds that the batteries are being considered for several medical applications, including defibrillators, artificial hearts, laptop oxygenators, diagnostic equipment, instrumentation, and blood and infusion pumps.—David Bowen

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