When talking about pure electric vehicles or plug-in hybrids, invariably the topic of batteries takes center stage and quite often dominates the discussion. And rightfully so since these batteries essentially are the lifeblood of the vehicle and also the limiting factor in just how far it can travel between charges. Vehicle acceleration and top speed on the open highway are not nearly as important as whether it keeps running until you arrive at your destination some 300 miles away. Maybe a 300-mile range is overly optimistic in the near term, but the distance you can travel between charges eventually has to match or better what you get now in your gas-only car.
From cell phones to laptop computers to electric cars, the technology of choice for powering these products today is Li-ion. In fact, Li-ion batteries are used in today's hybrid vehicles and are slated to power the new GM Volt scheduled to be introduced in 2010. However, being able to power a vehicle for 300 miles between charges currently is an elusive goal, but that may change if a company in Arizona is successful in its battery development.
Sion Power (www.sionpower.com) is using the combination of lithium and sulfur (Li-S) to develop a battery that will produce higher energy than currently is available with Li-ion. As noted on the company's website, the Li-S can produce more than 350 Wh/kg compared to 220 Wh/kg for Li-ion-type batteries. While the current Li-S battery technology only achieves a 170-mile driving range, work is underway at the company to increase the energy level to 450 Wh/kg which equates to 226 driving miles between charges. The company predicts that more than 600 Wh/kg specific energy can be achieved in the near future.
Not only will the distance traveled increase, but there are other benefits to using the Li-S technology. Again referring to the company's website, the battery module will weigh almost 200 lb less and have almost two times more vehicle payload than Li-ion. Also, the Li-S technology will be cost competitive and easy to produce.
The claim for reduced cost centers on the element sulfur which is cheaper than materials used in other battery technologies. Producing the Li-S cells should be on the same level of complexity as for Li-ion. The thickness and tensile strength of the anode and cathode also are similar and can be produced from the same raw materials. Furthermore, the company says some production equipment for Li-ion can be used without changes for Li-S.
Apparently, the company has attracted the attention of a major partner. According to a recent press release, BASF (www.basf.com) and Sion Power have entered into a joint development agreement to accelerate the commercialization of Li-S technology for electric vehicle applications. BASF is billed as the largest chemical company in the world with approximately 97,000 employees. The collaboration of the two companies should help improve the technology and bring the product to market sooner.
I doubt Li-S batteries will supplant Li-ion in vehicles in the foreseeable future, but for plug-in hybrids and electric vehicles, it's all about distance between charges. If all the claims for Li-S are realized, then the driving public has no reason not to embrace the electric vehicle as a true replacement for gas-only cars.
Paul Milo
Editorial Director
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