Battery for electric cars self-heats when it’s freezing

"We don't want electric cars to lose 40 to 50 percent of their cruise range in frigid weather ... and we don't want the cold weather to exacerbate range anxiety," says Chao-Yang Wang.  "In cold winters, range anxiety is the last thing we need." (Credit: Toyota UK/Flickr)

A new lithium-ion battery that self-heats could be the answer for electric car owners who drive in frigid weather and suffer from winter “range anxiety,” researchers say.

“It is a long standing problem that batteries do not perform well at subzero temperatures,” says Chao-Yang Wang, chair of mechanical engineering, professor of chemical engineering, and professor of materials science and engineering at Penn State.

“This may not be an issue for phones and laptops, but is a huge barrier for electric vehicles, drones, outdoor robots, and space applications.”

Conventional batteries at below freezing temperatures suffer severe power loss, which leads to slow charging in cold weather, restricted regenerative breaking, and reduction of vehicle cruise range by as much as 40 percent—problems that require larger and more expensive battery packs to compensate for the cold sapping of energy.

“We don’t want electric cars to lose 40 to 50 percent of their cruise range in frigid weather as reported by the American Automobile Association, and we don’t want the cold weather to exacerbate range anxiety,” said Wang.  “In cold winters, range anxiety is the last thing we need.”

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The all-climate battery weighs only 1.5 percent more and costs only 0.04 percent of the base battery. Researchers designed it to go from -4 to 32 degrees Fahrenheit within 20 seconds and from -22 to 32 degrees Fahrenheit in 30 seconds and consume only 3.8 percent and 5.5 percent of the cell’s capacity—far less than the 40 percent loss in conventional lithium ion batteries.

As described in the journal Nature, the battery uses a nickel foil of 50-micrometer thickness 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 electrons to flow through the nickel foil to complete the circuit to quickly warm the inside of the battery. Once the battery is at 32 degrees Fahrenheit, the switch turns off and the electric current flows in the normal manner.

While other materials could also serve as a resistance-heating element, nickel is low cost and works well, researchers say.

“Next we would like to broaden the work to a new paradigm called SmartBattery,” Wang says. “We think we can use similar structures or principles to actively regulate the battery’s safety, performance and life.”

Wang is the chief technology officer and founder of EC Power which supported the research.

Source: Penn State