Will Gas Pumps Ever Match the Speed of Electric Car Chargers?

Although electric vehicles are quickly gaining popularity, some potential owners are still wary. The slow rate of EV charging is a major factor.

However, far faster charging might be feasible in five to ten years. Companies are creating new “solid state” batteries that are more stable at higher charging rates, as well as new lithium-ion battery materials that are more stable. They could achieve recharge rates of no more than 20 minutes.

Meanwhile, a group of researchers recently created a prototype lithium battery that, when used in a lab setting, can be recharged more than 50% of the way in just three minutes and can do it thousands of times without noticeably degrading. According to the researchers, this could lead to the development of batteries that can fully recharge in as little as 10 minutes.

However, until ultra-fast-charging EV batteries are both technically possible and economically viable, there are still science and engineering obstacles to be addressed. And some experts wonder if EVs with such short charging times are really the future we desire, at least with the current electric system.

Powering up

Today’s EV batteries are made up of tens of thousands of lithium-ion cells, each of which has the capacity to store and discharge energy thousands of times. Each of those cells is made up of a liquid electrolyte in between two electrodes: a metal cathode and a graphite anode. Lithium ions fill the crevices between the graphite layers when the battery charges by moving through the liquid as it moves from the cathode to the anode, like wooden blocks.

How rapidly the battery charges depends on how quickly lithium ions flow from the cathode into the anode. But if lithium is shoved into the anode too quickly, issues start to appear, much as rapidly stacking pieces can make the structure unsteady.

Lithium batteries may overheat when being charged quickly, which will eventually lead to their degradation. More problematically, a condition known as lithium plating occurs when lithium begins to accumulate on the anode’s surface rather than inside it. Not only can this significantly diminish the battery’s capacity, but over time, the lithium deposits also produce dendrites, which are filament-like structures. Once they begin to form, those dendrites have the potential to cross the electrolyte, come into contact with the cathode, and produce a short circuit that might cause the battery to catch fire or blow up.

The 95 kilowatt-hour battery of an Audi E-tron SUV could theoretically be charged by a 350 kilowatt fast charging station, the most potent public charger currently accessible in the U.S., in around 16 minutes. However, the battery itself can only handle a maximum of 150 kilowatts of power, thus the real charging time is more like 40 minutes.

The rate at which a battery recharges in the real world varies on a number of factors, including the battery’s size, level of charge, and even the weather, in addition to the charger and the amount of power it can handle. (The charging speed decreases after a battery is 80% full to minimize damage to the battery.)

A future with ultra-fast charging?

While adding 200 miles of range in 15 minutes is quick, fueling up for a road trip in five minutes flat is still a long way off. Those wishing for a similar EV charging experience may want to wait for the upcoming battery advancements.

Niobium anodes store less energy per unit mass than traditional graphite anodes, therefore the speedy charge comes at a cost. Because EV manufacturers sometimes favor energy-dense batteries (which can be driven farther on a single charge) over ones that can be charged more quickly. In the future, it sees a version of these batteries being used in fleets of vehicles, where any downtime for recharging costs the business money.

New solid state battery designs hold potential for individual drivers seeking a greater jolt of kilowatts. In such batteries, a solid electrolyte, frequently made of ceramic, rather than a liquid one, conducts the lithium ions. This makes the battery safer because flammable liquid electrolytes are used. It also makes it possible to use various anode materials that are quicker to charge and more resistant to lithium plating.

Social speed restrictions

The viability of ultra-fast charging is uncertain, even if EV batteries that can charge in less than 10 minutes are technically feasible. Today’s fast charging stations already take a lot more electricity from the grid than the 120- and 240-volt outlets many EV owners use at home because they operate at 400 volts and higher. The grid could experience significant strain if all Americans drove EVs and expected to always have access to quicker charging.