Watts the Deal With Lithium-Ion Batteries?

Alternative-Fuel Vehicles Look to the New Technology


  • Toyota Prius

    Toyota Prius

    The future of the Toyota Prius as envisioned by the folks at Edrive Systems, makers of plug-in hybrid conversions. | March 18, 2010

3 Photos

Ten years ago, the idea of driving a mass-produced vehicle that could run on electricity seemed like science fiction, yet there are currently over a dozen gas-electric hybrid vehicles to choose from and more on the way. As climate change becomes an increasingly hot topic and our national addiction to oil appears in the news almost every day, alternative-fuel vehicles are entering the mainstream and electric power is leading the way.

Early electric vehicles (EVs) ran on lead acid batteries that were heavy and lacked sufficient power. As technology progressed, the industry moved to nickel metal hydride (NiMH) batteries that were much better suited to the task of propelling a vehicle. Today, with hybrid cars gaining ground and EVs just about to hit the market in earnest, a debate is under way as to whether lithium-ion batteries will (or should be) the next battery system to come into play. Although big names like Toyota and GM are racing to develop them, lithium-ion batteries have yet to be tested on the same mass scale as NiMH batteries. As such, they are not quite ready for prime time.

The Pros "Lithium has so much potential to be less expensive and has such a higher energy density than other types of batteries that I think it's the future" says Greg Hanssen, CEO of Edrive Systems, a company that retrofits Prius hybrids, allowing them to be plugged in. The energy density — the amount of energy that can be stored within a given space — is one of the biggest selling points of lithium-ion technology. Lithium-ion batteries have an energy density almost twice that of the NiMH batteries currently being used in hybrid vehicles and about six times the energy density of lead acid batteries, the units found in most conventional cars and in GM's ill-fated EV1. Take a vehicle with a 1,500-pound NiMH battery pack and replace it with a 1,500-pound lithium-ion pack, and you'll be able to go roughly twice as far without adding any weight. Or, put in a battery half the size and achieve the same mileage. Either way, you win.

Another plus for lithium-ion batteries, Hanssen points out, is cost. "While lithium is still expensive, it is dropping and at the same time the cost of nickel is rising. Over time, lithium prices will come down to the point where [the batteries] are cheaper. In an industry where automakers will try to shave 20 cents off the cost of a door panel, the price of the battery system can make a huge difference."

On an environmental level, lithium-ions are a big step forward as well. "Since lithium is a lighter element it is less toxic and therefore has less of an impact on the environment," points out Wally Rippel, the principal power electronics engineer for Tesla Motors, makers of the lithium-ion battery-powered Tesla Roadster. Rippel adds that since there is value in lithium it's in the best interests of the battery manufacturers to recycle them. Built into the cost of the Tesla is the price of reclaiming the battery packs, to ensure they will be recycled.

The Cons The primary concern regarding lithium-ion batteries is safety, fueled in part by the 2006 global recall of lithium-ion laptop batteries after a small number of them overheated or caught fire. Although overheating — or worse, fire — would be a concern to anyone driving a vehicle powered by a battery pack, Hanssen is quick to point out that "whenever you have a high concentration of energy in a very small package, the potential for that energy to react negatively is high," which is why battery packs are equipped with energy and heat sensors and computer safety nets so that the units will shut down should they become unstable.

"Any battery can blow up if treated improperly," he points out, adding that presently, people drive around sitting on top of canisters filled with highly flammable gasoline and think nothing of it. "If I were a consumer today buying a [gas-electric] hybrid, I'd be more concerned about the other drivers around me than I would about harm from the battery system."

The other unknown with transportation-related batteries is shelf life. Lithium-ion batteries used in laptops and cell phones have a shelf life of about three to four years. This tends not to be a problem because most people upgrade their gadgets before the batteries fail. But a car battery has to last much longer. Hanssen concedes that this is a concern and that a tremendous amount of improvement has been made in this area. "One of the things that we've learned is that completely charging and discharging these packs leads to a shortened lifespan, so most hybrids only allow the battery to charge as high as 80 percent and discharge down to 30 percent, which improves the lives of the cells significantly."

Another potential downside is that, according to an EV World article, "Peak Lithium?", 78 percent of the world's lithium carbonate is produced in just two places, Argentina and China. Furthermore, there is presently not enough lithium being produced globally to satisfy the demand for lithium-ion battery packs that a large-scale EV revolution would require, should it happen at all. As the auto industry moves forward, availability and market control will have to be taken into consideration, lest we find ourselves jumping from a rapidly diminishing petroleum supply to a rapidly diminishing lithium supply.

The Jury's Still Out The end run of all of this is that we will have to wait and see. Plug-in hybrids are on their way in one form or another and EVs like the Tesla are right around the corner as well. Due to the state of world politics and the environment, the public is demanding alternatives, and batteries will play a big part in that revolution. At the present time, cost, energy density and market demands for high-range vehicles place lithium-ion at the forefront of the next wave in EVs and hybrid cars. As to whether they will stand up to the test of daily high-mileage usage, only time will tell.

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