Electric car charging in just 10 minutes ? | New Lithium-Ion battery technology makes it possible

EV-fast-charging | Lithium-Ion battery technology | Asymmetric heating
P.C: Asymmetric Heat Modulation by Chao-Yang Wang Group

Being used to fueling cars in under 10 minutes for a 400 km range, it’s natural that every driver expects the same to happen with electric cars too. Is it technically feasible? Yes, this new battery technology could allow super-fast charging of lithium-ion batteries, up to 480 kilometers range in just 10 minutes, with almost no loss.

What is the problem with today’s EV batteries?

The Lithium-Ion batteries present in today’s electric vehicles can handle only a limited charging power. When certain threshold exceeds, a surface deposit of lithium will get formed on the graphite anode (refereed as lithium plating), which severely impair the function of the battery. This is the reason why all the electric car makers limit or cut-down their charging at around 80-90% total capacity of the battery.

However, to reduce the charging time of an electric car to around ten minutes, the batteries would have to withstand a charging power of 400 KW - so far this is impossible. So, the researchers have been looking for a method to prevent the lithium deposition even at high charging power - and have found it!.

Solution: Short-term heating of the battery

The solution for the decade long lithium plating issue seems surprisingly simple: short-term heating of the battery during fast charging, prevents the formation of inhibiting lithium deposits in the battery and thus preserves the performance!

When you heat the lithium-ion batteries so quickly and briefly, to about +60 degrees centigrade while charging, the lithium deposition reduces drastically - even at 400 KW of charging power. This could fill up enough electricity in ten minutes to reach 320 to 480 kilometers with the electric car.

P.C: Joule

💡Of course nothing is simple as it is said: The rapid heating must be done so quickly at a correct calculated time duration ; otherwise this process can only degrade the battery life more. If this elevated heat (+60 deg C), last longer, the structure of the electrolyte may get affected.

How this battery technology was tested?

Researchers embedded a thin nickel foil in the battery cell. One end of the foil is soldered to the anode and thus the negative pole, the other end sticks out of the cell and forms a third pole - the activation pole (ACT). Now, when the fast charging starts, the ACT pole is shorted to the positive pole of the battery and thus the current flows almost only through the nickel foil.

Within a few seconds, the nickel foil heats up strongly and heats the battery in less than a minute to 60 degrees. If the battery is then hot enough, the nickel circuit is disconnected and the charging current is now used completely to charge the battery. Through this hot charging the battery can withstand 400 kilowatts without forming lithium deposits.

💡 The critical factor in the whole process is that once charging is completed, the battery should be quickly cooled down to room temperature and remains cool even when discharged. This is critical, since this asymmetric temperature change prevents the structural change of the electrolyte. 

Stable even after 2,500 charging cycles

Test with the above approach was successful and stable with the below two scenarios:

➤ One of the popular plug-in hybrid cars’s battery with 9.5-amp hours and an energy density of 170 watt-hours per kilogram was successfully charged in ten minutes to 80% of its SoC. After 1,700 charging cycles, the test resulted at only 20% of its capacity!.

➤ An electric car battery with 209 kilowatt hours per kilogram retained after 2.500 fast charging cycles even 91.7% of its capacity.

This technology helps slow charging too

The temperature of battery increases even with today's’ normal, hours-long charging, which typically reduces the capacity of the battery over time. But if we use this Asymmetric Temperature Modulation (ATM) at slower charging, we can get a better life of batteries. So this invention is not only for super-fast charging; but also advantageous for the regular slow chargers.

"In addition to fast charging, this design allows us to limit the battery's exposure time to the elevated charge temperature, thus generating a very long cycle life" 
             - Senior author Chao-Yang Wang.

Next Goal: EV Charging in just under 5 minutes !!!

According to the researchers: "Overall, the major benefit of Asymmetric Temperature Modulation (ATM) is that it provides a solution for accelerating electro-chemical processes while effectively minimizing degradation of the material,". Their calculations and rapid brief heating method would be financially rewarding: Although the installation of nickel foil makes the battery by 0.47% more expensive, but at the same time eliminates costs for battery cooling, as they explained.

This charging technology could make a real fast charging of electric cars possible, so the researchers believe. The stay at the charging station would then hardly take any longer than drinking a cup of coffee. But Wang and his team have even more ambitious goal of charging an energy-dense electric vehicle battery in just under five minutes without damaging it!

Source & more information:

➤ Joule article, Asymmetric Temperature Modulation for Extreme Fast Charging of Lithium-Ion Batteries , published on :October 30, 2019

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