Winter applications for self-heating battery

Researchers from Pennsylvania State University and EC Power have developed a lithium-ion battery that self-heats if the temperature drops below 0°C.

The ‘all-climate battery’, described in the journal Nature, 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 above freezing, the switch turns off and the electric current flows as normal.

(Credit: Chao-Yang Wang, Penn State)
(Credit: Chao-Yang Wang, Penn State)

“It is a long standing problem that batteries do not perform well at sub-zero temperatures,” said Chao-Yang Wang, a multidisciplinary engineer at Penn State, as well as CTO and founder of EC Power. “This may not be an issue for phones and laptops, but is a huge barrier for electric vehicles, drones, outdoor robots and space applications.”

According to the researchers, freezing temperatures cause conventional batteries to suffer severe power loss, resulting in slow charging, restricted regenerative braking and a reduction in vehicle range of up to 40 per cent. To compensate for this sapping of energy, electric vehicles are often equipped with larger and more expensive batteries. However, the all-climate battery weighs just 1.5 per cent more than the base battery. Furthermore, it uses 5.5 per cent of its charge warming itself from -30°C to 0°C, a process that takes around 30 seconds.

“We don’t want electric cars to lose 40 to 50 per cent 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,” Wang said in a statement. “In cold winters, range anxiety is the last thing we need.”

Wang said the next steps for the team will involve a broader project called SmartBattery, where similar principles are used to actively regulate battery safety, performance and life.