Thursday, February 22, 2018

Existing EV Batteries Could be Recharged 5 Times Faster

Lithium-ion batteries have massively improved in the last half-decade, but there are still issues. The biggest, especially for EVs, is that charging takes too long to make them as useful as regular cars for highway driving. Researchers from the University of Warwick (WMG) have discovered that we may not need to be so patient, though. They developed a new type of sensor that measures internal battery temperatures and discovered that we can probably recharge them up to five times quicker without overheating problems.

Overcharging a lithium-ion battery anode can lead to lithium buildup, which can break through a battery's separator, create a short-circuit and cause catastrophic failure. That can cause the electrolyte to emit gases and literally blow up the battery, so manufacturers impose strict charging power limits to prevent it.

Those limits are based on hard-to-measure internal temperatures, however, which is where the WMG probe comes in. It's a fiber optic sensor, protected by a chemical layer that can be directly inserted into a lithium-ion cell to give highly precise thermal measurements without affecting its performance.

The team tested the sensor on standard 18650 li-ion cells, used in Tesla's Model S and X, among other EVs. They discovered that they can be charged five times faster than previously thought without damage. Such speeds would reduce battery life, but if used judiciously, the impact would be minimized, said lead researcher Dr. Tazdin Amietszajew.

Faster charging as always comes at the expense of overall battery life but many consumers would welcome the ability to charge a vehicle battery quickly when short journey times are required and then to switch to standard charge periods at other times.

There's still some work to do. While the research showed the li-ion cells can support higher temperatures, EVs and charging systems would have to have "precisely tuned profiles/limits" to prevent problems. It's also not clear how battery makers would install the sensors in the cells.

Nevertheless, it shows a lot of promise for much faster charging speeds in the near future. Even if battery capacities stayed the same, charging in 5 minutes instead of 25 could flip a lot of drivers over to the green side.

Information & Image Source 2018.02.22

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