Extreme temperatures can seriously compromise the performance of lithium batteries. We've seen a number of developments promising to reduce the risk of them overheatingand catching fire, but at the other end of the scale, freezing temperatures aren't too friendly either, often leading to substantial power loss. In an advance that could have ramifications for everything from electric vehicles to space exploration, researchers have built a lithium battery that warms itself up to battle the winter chill.
While a battery that maintains its performance in cold temperatures could prove useful in many applications, including space travel and high-flying drones, in the eyes of Penn State University researchers, alleviating range anxiety for electric vehicles is one of the more promising. The power loss suffered in electric vehicles at below freezing temperatures can result in slow charging, impact regenerative braking and cut cruising range by as much as 40 percent.
We have seen EV manufacturers take steps to address these drawbacks. In 2010, for example, Ford announced an all-electric Focus with a thermal management system, which either heats or chills a coolant and pumps it through the battery system to regulate the temperature. But by and large, cold environments still present a real challenge to the performance of electric vehicles.
The Penn State team approached this problem by fitting a lithium battery with a nickel foil attached at one end to the negative terminal. An integrated temperature sensor reroutes the current through the nickel foil, warming the battery from the inside through resistance heating until it returns to above freezing temperature, and then switches off and leaves the battery to function normally.
In testing, the battery was able to warm from -4 ° Fahrenheit up to 32 ° F (-20 ° C to 0 ° C) in 20 seconds, and - 22 ° F to 32 ° F (-30 ° C to 0 ° C) in 30 seconds. And it did so while consuming just 3.8 percent and 5.5 percent of the battery's capacity respectively. By comparison, the team points out, this is a significant improvement on the 40 percent loss of capacity experienced by conventional lithium batteries in cold temperatures. In addition, the Penn State battery is only 1.5 percent heavier and costs 0.04 percent more than a conventional lithium-ion battery.
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