Cold behavior or range – what will play a greater role in the future development of electromobility?

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A critical aspect discussed in every redesign of traction batteries for electric vehicles is their low-temperature behavior. What might seem like a minor issue holds significant importance for the overall design and further development of an electric vehicle.

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Lithium-ion batteries, as used in nearly all electric vehicles and countless mobile devices today, are highly responsive to temperature fluctuations. But why does their performance decrease significantly in cold temperatures? There are primarily three reasons:

Internal resistances: At lower temperatures, internal resistances in the battery increase. This happens because the movement of lithium ions generating electric current slows down. This heightened resistance requires more energy to charge the battery and results in less energy available during discharge.

Chemical reactions: Battery performance relies on chemical reactions, which occur more slowly at lower temperatures. Particularly, the exchange of lithium ions between the anode and cathode, enabling the flow of charge, slows down, leading to reduced battery performance.

Charging efficiency: Battery charging efficiency also decreases in colder temperatures. This means it takes longer to charge the battery, and a full charge can store less energy compared to higher temperatures.

What options are available to enhance battery performance in winter?

Active heating of batteries is necessary to achieve optimal performance. Whether it’s pre-conditioning before starting the journey or in the initial kilometers until the cell temperatures are adequate. Some vehicles, such as our new Aiways U6 SUV-Coupé, include systems that warm the batteries to an optimal operating temperature before a planned charging stop to achieve the highest charging efficiency. However, all these systems consume additional energy, reducing the overall range.

Other cells are less temperature-sensitive

Apart from the widely used nickel-cobalt-manganese cell chemistries (NCM), there are batteries that are less sensitive to cold temperatures. Sodium batteries, for instance, do not exhibit the same behavior in cold conditions and could be an attractive alternative in colder regions. However, their energy density is lower than that of lithium-ion batteries, leading to a reduced range.

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The challenge lies in finding a balance: should we prioritize maximum range overall, or switch to sodium batteries in cold regions?

This dilemma raises central questions that the industry must answer in the coming years.