One of the things you might not learn about electric vehicles (EV) until you live with one is that they charge slower in cold temperatures, which means you might have to spend longer at a charging station on long winter drives.
In addition, the climate’s impact on your car’s battery chemistry, and the power drawn when you heat the cabin and seats can together sap about 25% of range when you’re cruising at 70 mph (113 km/h), compared with driving at that speed in mild weather.
Researchers at the University of Michigan have a way to tackle the first problem. By slightly altering the manufacturing process for lithium-ion EV batteries, their technique can enable rapid charging at awfully low temperatures – up to five times as fast – without reducing their energy density.
Marcin Szczepanski / University of Michigan Engineering
To be precise, the team’s method enables ‘6C’ charging at temperatures as low as 14 °F (-10 °C). The ‘C’ here is a way to express the charging speed relative to the battery’s capacity. So, for example, for a car with a 50-kWh battery, a 1C charging rate would mean charging at 50 kW, and a 6C charging rate would mean charging at 300 kW (6 × 50 kW). That’s ridiculously fast – and potentially good news for future EV owners in cold climes.
Why do cars charge more slowly in the cold? It’s because the movement of lithium ions back and forth between electrodes via a liquid electrolyte in a battery slows down. This reduces both the charging rate as well as the battery’s power.
So how do you speed up EV charging? One way is to follow researcher Neil Dasgupta’s method of laser drilling tiny pathways in the graphite anode that receives lithium ions during charging.
You’ll find that that this works well at room temperature, but in the cold, a chemical plating of lithium formed on the surface of the anode and prevented it from reacting with the electrolyte. So you’ll need to go one step further.
By coating the laser drilled graphite anode with a glassy material made of lithium borate-carbonate, charging can be sped up by five times the rate observed in below-freezing temperatures. The team published a paper documenting this work in the journal Joule last month.
The researchers note that this has the potential to address one of the major concerns cited by adults in the US surveyed by the American Automobile Association (AAA) last year about interest in purchasing EVs. They intend to explore ways to integrate their method into battery manufacturing processes – so hopefully, we’ll soon see electric cars that charge as quickly in the cold as they do in more pleasant weather.
Source: University of Michigan