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Although Tesla and Chevrolet now offer electric cars that can travel nearly as far on a charge as a gasoline-powered car can go on a tank of fuel, the recharge time for EVs has yet to achieve a similar breakthrough. Even Tesla’s ability to recharge a claimed 80 percent of its cars’ huge battery packs in as little as 30 minutes is a far cry from the time it takes to fill a tank with gasoline. Now, electronics maker Toshiba has announced it has begun work on a new type of lithium-ion battery geared toward electric cars that can be recharged much, much faster.
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The Problem
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According to Toshiba, the weak link in today’s lithium-ion batteries, like those used in the Chevrolet Bolt EV (which is capable of DC fast charging) and the Tesla Model S, X, and 3, is the anode portion of the cells. This is the negatively charged electrode, which in most modern lithium-ion batteries is a carbon-based material. During charging and discharging of the battery, ions move between the anode and the cathode, or positively charged electrode.
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This ion transfer enables the battery to release or take on energy; if you speed up the process too much (as when trying to charge or discharge a battery very quickly), it can suffer excessive degradation. Over time, the transfer of lithium metal between the anode and the cathode can cause increasingly uneven surfaces. Fast charging speeds this up, eventually leading to so much buildup that it can break the separator and bridge the two, causing a short—the exciting consequence of which is thermal runaway (that’s fire).
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Toshiba’s Solution
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This degradation is exactly what Tesla balances against speed with its ultrafast Supercharger DC chargers, which add energy to batteries very quickly at first before leveling off their rate of charge as the battery fills up. Working from an empty battery, Tesla’s chargers can only fast-charge for about 30 minutes, netting around an 80 percent charge. Filling up the remaining 20 percent can take as long or longer than the first 80 percent. (Not all EVs’ recharge times are battery limited; those equipped with onboard AC-to-DC chargers are slowed by that conversion process.)
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Toshiba’s solution aims to cut the recharge time drastically, to just six minutes for a 32-kWh pack good enough for an estimated 200 miles of driving range in a “compact EV.” The company doesn’t clarify whether that six-minute juice represents the battery’s full charge or a partial charge like Tesla’s 30-minute blast. Either way, that range is roughly equivalent to the distance one could cover with an 80 percent charge in the (larger than compact) Tesla Model S with either the 85- or 90-kWh battery pack.
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- 2017 Chevrolet Bolt EV Tested: Electric Car 2.0
- 2016 Tesla Model X Tested: More Than Its Silly Falcon Doors
- 2015 Tesla Model S P90D Tested: The First Sub-3.0-Second Sedan We’ve Ever Tested
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Toshiba’s advancement focuses on the lithium-ion cells’ anodes. In place of the lithium-titanium oxide anodes the company uses on its current-generation lithium-ion batteries, there are titanium-niobium oxide (TNO) pieces. Combined with a method for storing lithium ions “more efficiently in the [cell’s] crystal structure,” TNO anodes are claimed to double the energy capacity of Toshiba’s current offerings. Initial testing has revealed the new cells maintain “over 90 percent” of their capacity after 5000 cycles with the ability to be rapidly charged, even in cooler temperatures as cool as 14 degrees Fahrenheit (where the charge time increases slightly, to 10 minutes). Perhaps most important is that Toshiba promises that these lithium-ion cells with the TNO anode will be available in 2019.
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