As we’ve consistently pointed out, charging battery-electric cars at home, at night, is incompatible with photo-voltaic generation peaks, so this energy tends to be generated by fossil fuel plants. Furthermore, electric vehicles still have short-range, long charging times, and limited battery lives. But researchers at Penn State are on the way to solving some of these problems. For instance, electric vehicle owners may soon be able to pull into a fueling station, plug their car in, go to the restroom, get a cup of coffee and in 10 minutes, drive out with a fully charged battery.
Fast charging is the key to enabling the widespread introduction of electric vehicles.
The Penn State team recently demonstrated a way to charge an electric vehicle in ten minutes for a 200-to-300-mile range. And they were able to maintain this performance over 2,500 charging cycles, or the equivalent of half a million miles of travel.
Lithium-ion batteries degrade when rapidly charged at ambient temperatures of under 50 degrees Fahrenheit. Why? Because, rather than the lithium ions smoothly being inserted into the carbon anodes, the lithium deposits in spikes on the anode surface. This lithium plating reduces cell capacity and also causes electrical spikes and unsafe battery conditions.
Batteries heated above the lithium plating threshold, whether by external or internal heating, do not exhibit lithium plating. As reported in the journal Joule, the team realized that if the batteries could be heated up to 140 degrees Fahrenheit for only 10 minutes and then rapidly cooled to ambient temperatures, lithium spikes would not form, and heat degradation of the battery would also not occur. And, the rapid cooling of the battery is accomplished using the cooling system designed into the car.
The 10-minute charging is essential for the adoption of electric vehicles because it solves the “range anxiety problem.
The self-heating battery uses a thin nickel foil with one end attached to the negative terminal and the other extending outside the cell to create a third terminal. A temperature sensor attached to a switch causes the electron to flow through the nickel foil to complete the circuit. This rapidly heats the nickel foil through resistance heating and warms the inside of the battery.
The U.S. Department of Energy supported this work.