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Idaho National Laboratory

From the INEEL Archives
Feature Story

Power Play - INEEL scientists develop long-lasting battery for reconnaissance missions

Contributed by Ethan Huffman
October 2002
INEEL scientist Mason Harrup

INEEL scientist Mason Harrup has formulated a solid polymer electrolyte that could revolutionize the battery industry.

In early January, 75 members of America’s elite Special Operations Force commandos spent eight days behind enemy lines gathering military information and conducting raids on Taliban and Al-Qaida hideouts in the Zawar Kili region of Afghanistan. Equipped with the most technically advanced gadgetry for their mission including laptops, night vision goggles and remote surveillance items, they proceeded to identify cave complexes and secret tunnels before calling in air strikes. Although the mission was successful, at least one element hindered their ability to remain on the ground longer and continue with their strategic reconnaissance mission. That element was battery power.

Today’s military, including much of the work done by Special Operations forces, rely on portable, battery-powered equipment. Commandos often employ devices such as GPS receivers, smart missiles and chemical agent monitors. The challenge is to supply advanced equipment with a reliable battery that can perform for extremely long hours in a variety of weather conditions.

Everyday alkaline batteries are not capable of meeting these stringent requirements. Even the more advanced lithium-ion rechargeable batteries run out of power within a few days. However, battery research and development being done at the INEEL is revolutionizing the internal makeup of batteries and could substantially improve the length of time a battery lasts.

Such developments have garnered a keen interest from military and national security officials who see great potential for the use of these new lithium-solid electrolyte batteries in future intelligence missions.

HOW BATTERIES WORK

INEEL scientist Mason Harrup

Harrup holds a lithium anode coated with the solid polymer electrolyte. The polymerís chemical makeup works as an insulator for electrical currents, but maintains the ability to conduct positive ions.

A typical battery can be thought of as having three compartments or fields, the anode, the electrolyte and the cathode. The secret to an ordinary battery’s success involves the chemical reaction that occurs inside the anode. When an electronic device is turned on, a complete circuit is made, and negatively charged electrons flow from the anode, out into the electronic device giving it power, and back into the battery’s cathode. At the same time, positive ions are also being sent from the anode to the cathode via the electrolyte field. As electrons and ions build up in the cathode, the battery begins to lose its power.

The amount of time it takes for a battery to run out of power depends on two properties. The first, is the amount of power used up when an electrical device is turned on. The second, however, occurs because of a concept known as "battery drain."

Most everyday alkaline batteries use a liquid-based solution or paste electrolyte. Battery drain occurs because the liquid electrolyte is electrically conductive and allows electrons and ions stored in the anode to pass through freely, even when the device is turned off. Since both the electrons and ions can move through the electrolyte, the battery runs down while it is still off.

In fact, some batteries can lose up to 15 to 20 percent of their power in a single day even when they are not being used. This may explain why a cordless phone will go dead overnight even if it is not used, but left off the charger. It also explains why high-power devices, such as those used by the military, must have their batteries replaced or recharged every few days even if they are not always on.

According to Mason Harrup, an INEEL chemist, "Even if you only talk on a radio two minutes a day and then turn the device off, the battery will still lose power because electrons and ions will drain through the highly conductive liquid electrolyte field. Within a few days batteries lose so much power they have to be recharged or replaced."

While technology advancements have allowed more and more gadgetry to become portable, there has been a stalemate in the advancements of long-lasting batteries.

For Special Operations missions, batteries that can run specialized electronic equipment for longer periods of time could mean the difference between life and death for soldiers and civilians. That’s why military and national security officials are excited about the work being done at the INEEL.

WHAT’S GOING ON AT THE INEEL?

Five years ago, several INEEL scientists made an impressive discovery. While working on another project, they formulated a solid composite electrolyte, based upon the polymer MEEP ([bis(methoxyethoxyethoxy)phosphazene]), which conducts positive ions very well, yet also stops negatively charged electrons. The polymer’s chemical makeup works as an insulator for electrical currents, but maintains the ability to conduct positive ions. Therefore, electrons can’t leak through the electrolyte causing the battery to lose additional power. According to Harrup, who discovered the electrolyte, this new electrolyte could revolutionize the battery industry. "Basically, the chemical makeup is such that the electrolyte could allow batteries for electronic devices such as laptops and cell phones to sit unused for up to 500 months between charges," said Harrup.

According to Harrup, the new battery is more efficient, using power only when the device is physically on. That could mean that batteries transported from the U.S. to Afghanistan, for instance, could remain fully charged without losing any power during the trip. It could also mean that radios, laptops, or other electronic devices that are used for short periods of time in field and then turned off wouldn’t lose any power until they were turned back on.

And because the polymer begins in a liquid state, it could be molded to meet virtually any application or battery size.

Harrup and his team are currently perfecting the polymer so it can be outfitted for high-drain electronic devices such as laptops, cell phones, GPS units, and other military and consumer goods. The team is looking into ways to improve the routes positive ions take when they travel through the electrolyte. Right now, too few ions travel through the electrolyte at one time to meet the demands of high-drain devices such as cell phones or laptops.

Batteries built with the current generation of this polymer composite, however, are capable of running low-drain devices such as watches and pacemakers that require a constant supply of energy over an extended period of time.

"We feel that in the foreseeable future, maybe in the next two to four years, we’ll have a battery capable of running a high-drain device," said Harrup.

HOW THEY ARE MADE

The solid electrolyte produced at the INEEL is a combination of a unique liquid polymer and a ceramic powder. When properly mixed, a translucent, nontoxic, flexible electrolyte membrane is produced.

In the past, other researchers have made attempts at using similar polymers, called polyphosphazenes, in battery construction. Until now, researchers have been unsuccessful in strengthening the liquid polymer to hold its shape. This is critical because the electrolyte must also serve to physically separate the electrodes or the battery will short out and immediately "die" - sometimes with explosive results.

At the INEEL, Harrup and his team used the ceramic powder to form a skeletal structure around the conductive portions of the liquid polymer. When dried, the ceramic powder becomes flexible and sturdy, while the conductive portions of the polymer weave throughout the structure like ribbons. The combined elements allow the electrolyte to transfer positively charged ions easily, but prevent negatively charged electrons from leaking through, draining the battery.

Longer-lasting power is not the only benefit of these batteries. The solid electrolyte inside will eventually replace the liquid solution, generally composed of sulfuric acid or toxic organic chemicals, found in conventional batteries. The team is designing the new batteries so they can be exposed to extreme elements such as adverse weather climates, humidity and pressure fluctuations without the fear of a toxic or dangerous leak occurring. The batteries are also expected to weigh less than conventional batteries.

THE NEXT STEP

To date, Harrup and his team have secured one patent, an Energy@23 and a Bright Light award for their work. Currently, two more patents have been submitted for approval, and a fourth is being prepared.

"We feel that the future is very bright for these batteries. Most of the technical challenges have been met in the laboratory setting, and the process of obtaining the patents needed to protect our invention are well underway," said Harrup. "Now we have to begin to address the issues related to making and marketing a practical battery."

As U.S. Special Operations and other military missions continue throughout the world, and as more technology becomes portable, the need for an energy source that can meet modern-day challenges exists. With any luck, the future development of a long-lasting battery looks bright indeed.

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