Electric car owners may soon be able to fully charge their vehicles in just 10 minutes, thanks to a new self-heating battery developed by researchers. "We demonstrated that we can charge an electrical vehicle in ten minutes for a 200 to 300 mile range," said Chao-Yang Wang, a professor at Pennsylvania State University in the US. "And we can do this maintaining 2,500 charging cycles, or the equivalent of half a million miles of travel," Wang said.
Lithium-ion batteries degrade when rapidly charged at ambient temperatures under 10 degrees Celsius. This is because, rather than the lithium ions smoothly being inserted into the carbon anodes, the lithium deposits in spikes on the anode surface, the researchers explained.
This lithium plating reduces cell capacity, but also can cause electrical spikes and unsafe battery conditions, according to the research published in the journal Joule.
Researchers noted that batteries heated above the lithium plating threshold, whether by external or internal heating, will not exhibit lithium plating.
The team had previously developed their battery to charge at 10 degrees Celsius in 15 minutes.
Charging at higher temperatures would be more efficient, but long periods of high heat also degrade the batteries, the researchers noted.
"Fast charging is the key to enabling wide spread introduction of electric vehicles," said Wang.
Wang and his team realised that if the batteries could heat up to 60 degrees Celsius for only 10 minutes and then rapidly cool to ambient temperatures, lithium spikes would not form and heat degradation of the battery would also not occur.
"Taking this battery to the extreme of 60 degrees Celsius is forbidden in the battery arena," said Wang.
"It is too high and considered a danger to the materials and would shorten battery life drastically," he said.
The rapid cooling of the battery would be accomplished using the cooling system designed into the car, Wang explained.
The team noted that large difference from 60 degrees to about 24 degrees Celsius will also help increase the speed of cooling.
"The 10-minute trend is for the future and is essential for adoption of electric vehicles because it solves the range anxiety problem," said Wang.
The new 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 electrons to flow through the nickel foil to complete the circuit, according to the researchers.
This rapidly heats up the nickel foil through resistance heating and warms the inside of the battery, they said.