'Quantum charging' would reduce EV charge time

Despite vast improvements in battery technology, today’s electric vehicles (EVs) still take about 10 hours to fully recharge at home, and even the fastest superchargers at the charging stations require up to 20–40 minutes. To address this problem, scientists looked for answers in the field of quantum physics — and discovered that quantum technologies may promise new mechanisms to charge batteries at a faster rate.

The concept of a ‘quantum battery’ was first proposed by Alicki and Fannes in 2012, where it was theorised that quantum resources, such as entanglement, can be used to vastly speed up the battery charging process by charging all cells within the battery simultaneously in a collective manner. This is particularly exciting as modern large-capacity batteries can contain numerous cells. Such collective charging is not possible in classical batteries, where the cells are charged in parallel independently of one another.

The advantage of this collective versus parallel charging can be measured by the ratio called the ‘quantum charging advantage’. Around the year 2017, it was noticed that there can be two possible sources behind this quantum advantage — namely ‘global operation’ (in which all the cells talk to all others simultaneously) and ‘all-to-all coupling’ (every cell can talk with every other, but every discussion has only two participants). However, it is unclear whether both these sources are necessary and whether there are any limits to the charging speed that can be achieved. Scientists at Korea’s Institute for Basic Science (IBS) recently explored these questions.

In a study published in the journal Physical Review Letters, the scientists showed that all-to-all coupling is irrelevant in quantum batteries and that the presence of global operation is the only ingredient in the quantum advantage. The group went further to pinpoint the exact source of this advantage while ruling out any other possibilities and even provided an explicit way of designing such batteries.

In addition, the group was able to precisely quantify how much charging speed can be achieved in this scheme. While the maximum charging speed increases linearly with the number of cells in classical batteries, the study showed that quantum batteries employing global operation can achieve quadratic scaling in charging speed. To illustrate this, consider a typical electric vehicle with a battery that contains about 200 cells. Employing this quantum charging would lead to a 200 times speed-up over classical batteries, which means that at-home charging time would be cut from 10 hours to about 3 minutes. At high-speed charging stations, the charge time would be cut from 30 minutes to mere seconds.

The researchers say the implications of quantum charging go well beyond electric cars and consumer electronics; for example, it may find key uses in future fusion power plants, which require large amounts of energy to be charged and discharged in an instant. And while quantum technologies are still in their infancy and there is a long way to go before these methods can be implemented in practice, it is believed that quantum batteries could revolutionise the way we use energy and take us a step closer to a sustainable future.

Image caption: A pictorial illustration of today’s electric vehicle versus the future vehicle based on quantum battery technologies.

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