Owners of e-cars have already had the tolerable experience: the lithium battery dies on very cold winter days and hot summer days.

Because the storage capacity decreases both at low temperatures and at excessive heat.

The result: lithium batteries discharge faster and lose performance.

The range of a car is reduced.

In order for battery systems to function without problems in winter, they are usually equipped with a heater or thermal insulation.

In summer, a cooling system protects against overheating.

However, this increases the weight of a vehicle.

However, each additional device must also be supplied with power from the battery, which is at the expense of the range.

A new type of battery could possibly make heating or cooling superfluous.

Manfred Lindinger

Editor in the department "Nature and Science".

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As researchers from the University of California in San Diego report in the “Proceedings” of the American National Academy of Sciences, the rechargeable battery still has 87.5 percent of its original capacity at minus 40 degrees, and the capacity even increased slightly at plus 50 degrees .

Energy losses during charging and discharging are virtually non-existent.

Conventional lithium batteries can no longer be used under these conditions because their liquid electrolyte solidifies or evaporates.

Most batteries are therefore only designed for a temperature range between 0 and a maximum of 40 degrees.

A failure can only be prevented with special measures.

To make their power source resistant to cold and heat, Zheng Chen and his colleagues used a mixture of a sulfur and fluorine-containing lithium salt and dibutyl ether as the electrolyte.

The organic substance solidifies at minus 95 degrees and vaporizes at plus 141 degrees.

The material therefore remains liquid and therefore conductive at low and high temperatures.

Lithium ions can continue to move freely in the electrolyte even at extreme temperatures.

According to the researchers, the electrolyte is particularly suitable for lithium-sulphur batteries.

A promising prototype

These batteries are among the next-generation rechargeable batteries because they are potentially more powerful than classic lithium-ion batteries and, unlike these, do not require expensive materials.

The cathode consists of sulfur instead of a cobalt-containing mixed oxide, which is held together and stabilized by a polymer.

Pure sulfur tends to decompose quickly in battery operation.

Metallic lithium, which has a very high energy density, is used for the anode.

However, when charging the battery, there is usually a risk that the lithium will not be deposited evenly on the anode, but will instead grow in the form of dendrites.

These can lead to a short circuit and destroy the battery.

The danger is particularly great at high temperatures, because the electrochemical reactions in common electrolytes take place in an uncontrolled manner.

The risk of dendrite formation does not exist with the ether electrolyte, however, since the conductivity is high even at high temperatures, write the researchers led by Chen.

A prototype in pouch cell format proved to be stable at room temperature even after 50 charging and discharging cycles and did not show any significant loss of performance.

At an ambient temperature of plus 50 degrees, it was still 30 cycles.

This is by far not enough for practical applications.

This requires at least a thousand charging and discharging cycles.

The researchers now want to optimize the cell chemistry so that the battery runs more stably and longer even at higher temperatures.

Then the cold and heat tolerant lithium-sulphur battery could also reliably supply electricity in Siberia or the Sahara.

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