One of several presenters at this year’s sixth annual Electric Aircraft Symposium held by the CAFE Foundation at Santa Rosa, California on April 27 and 28 this year, Dr. Winfried W. Wilcke, senior, Manager of Nanoscale Science and Technology at IBM’s Almaden Research Center, initiated and heads up the Battery 500 project, a coalition to create a battery that will give electric cars a 500-mile range. Partners include the United States Department of Energy National Laboratories, the Stanford Linear Accelerator National Laboratory, and Stanford University. Asahi Kasei and Central Glass have recently joined the enterprise, chosen for their expertise in battery separator membranes and electrolytes respectively. The Project’s goal is to eliminate range anxiety for EV owners and use the excess capacity of the electrical grid at night for charging.
Dr. Wilcke explained that if all U. S. drivers had battery-powered electric cars, 73 percent of those EVs could be recharged at night with excess electricity from the grid. Given a typical week for a 500-mile car, a 4 kilowatt home charger used 5 nights out of that week would keep the car on the road with no need for public charging stations or unnecessary stops.
Because Lithium-air cells literally pull their reagent, or reactive element, out of the air, such batteries can achieve up to 1000 Watt-hours per kilogram while weighing considerably less than their solid electrode cousins. Current Lithium-ion cells achieve 100-200 wh/kg, according to Dr. Wilcke, limiting their range partly because of weight considerations.
It’s important that these batteries are rechargeable, because most metal-air batteries are primary, or non-rechargeable cells, and would not readily lend themselves to disposal at the end of trip. Equivalent lead-acid batteries would weigh 15,900 grams (15 pounds), Lithium-ion 2,200 grams (4.84 pounds) and Lithium-air 300 grams (0.66 pounds) for the same range. Electrolyte choice is critical, since two different electrolytes help the battery achieve its high range, and both need to be capable of surviving multiple charge/discharge cycles.
Argonne National Labs’ petaflop IBM Blue Gene supercomputer helped model the interactions of all the components of the battery.
In a final illustration of fossil fuel to electric energy densities, Dr. Wilcke explained that filling up his Beech King Air required 384 gallons of Jet A, weighing 2,575 pounds and costing $2,112. Even an equivalent pack of 1,200 wh/kg batteries would weigh 6,233 pounds. Dr. Wilcke pronounced, “No joy” for that scenario, just a reflection of how far we have to go to achieve practical electric aviation.