ARCHIVED - Getting the Next Generation of Batteries Ready for the Road

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May 07, 2007— Ottawa, Ontario

From a small, robust power source for a life-saving pacemaker to a giant bank of cells for storing the electricity generated by a windmill, batteries have become an indispensable part of our lives. And they promise to become even more important, helping us wean our economy from the unsustainable use of fossil fuels, consumed in millions of vehicles every day.

Pouch cell assembly
Pouch cell assembly

We have better things to do with fossil fuels than burn it in vehicles, and NRC researcher Dr. Isobel Davidson envisions better ways of moving us around. As the leader of a project on advanced electrical storage at the NRC Institute for Chemical Process and Environmental Technology (NRC-ICPET), she is looking at how to make the next generation of batteries ready for the road.

That means more than merely mating electrical storage with a conventional gasoline engine to create the hybrid systems that are now starting to multiply in the automotive marketplace. The NRC team is preparing for the next step: a plug-in hybrid electric vehicle (pHEV) that will rely on the charge of the battery on board, which a user could replenish at the nearest available electrical outlet.

Battery cycler
Battery cycler

But for pHEVs to become a practical alternative, battery technology must evolve to meet the task. Today's most popular model, which stores energy using lithium ions, just will not do. "Most people are pretty happy with lithium ion batteries in their cell phones or laptops, but when you put them in a vehicle, you have two things to worry about," says Dr. Davidson: "safety and durability."

The organic-based solvent that enables lithium batteries to store an electric charge is flammable and volatile, she explains. It packs a great deal of energy into a very confined space. But if the container is abused – for example, if it's pierced with a metal object – the result can be a minor explosion and fire. And in the event of a vehicle collision, there could be a major explosion and fire. Dr. Davidson and her colleagues are therefore examining a range of more benign solvents that could yield the same electrochemical properties.

One of the most likely candidates is succinonitrile, a waxy plastic-like concoction. When melted and mixed with appropriate salts, the result is a compound that conducts lithium ions but not the electrons themselves, and so enables a battery to hold its charge. Succinonitrile is one of several materials that NRC-ICPET researchers are combining with lithium salts in their search for electrolytes that are non-flammable, non-corrosive, electrochemically stable, and above all, inexpensive. On any given day in the team's laboratory, various recipes are inserted into small circular test cells appropriately known as "coin cells", with dozens of samples tested.

In much the same way, Dr. Davidson's team also seeks new materials for cathodes, hoping to find a worthwhile substitute for the increasingly expensive cobalt that is commonly used in lithium batteries. Replacements such as manganese oxides or iron phosphate are emerging as prospects. But as with electrolytes, the goal is to find a combination that can match the demanding performance requirements of pHEVs.

And however daunting that goal may seem, Dr. Davidson insists that it is well worth achieving. She points to a recent study by the US Department of Energy — which is also interested in this technology — showing that if most of North America's automotive fleet was converted entirely to pHEVs, the vehicles could be sustained on today's electrical generating grid by taking advantage of the unused capacity during the system's overnight, "off peak" hours.

Canada is especially well placed to adopt this strategy, since so much of our electricity is generated by hydroelectric or nuclear power, rather than from hydrocarbon sources such as oil, natural gas or coal. In fact, concludes Dr. Davidson, the advent of battery technology associated with the pHEV could change how we view fuel.

"It allows you to use electrons as fuel for transportation," she says. This possibility would reduce pollution, minimize the production of climate-altering greenhouse gas emissions, and save our valuable fossil fuels for other applications.

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