Self-heating Li-ion battery eases winter range anxiety for EV owners

Self-heating Li-ion battery eases winter range anxiety for EV owners

By eeNews Europe

"It is a long standing problem that batteries do not perform well at subzero temperatures," says Chao-Yang Wang, William E. Diefenderfer Chair of mechanical engineering, professor of chemical engineering and professor of materials science and engineering and director, Electrochemical Engine Center. "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%, the researchers pointed out in the journal Nature. The problems 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% 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," says Wang. "In cold winters, range anxiety is the last thing we need."

The researchers, relying on previous patents by EC Power, developed the all-climate battery to weigh only 1.5% more and cost only 0.04% of the base battery. The researchers also designed the battery to go from -20 to 0 degrees C within 20 seconds and from -30 to 0 degrees C in 30 seconds and consume 3.8% and 5.5% of the cell’s capacity. This is far less than the 40% loss in conventional lithium ion batteries.

The all-climate 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. This rapidly heats up the nickel foil through resistance heating and warms the inside of the battery. Once the battery is at 0 degrees C, 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.

"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."

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