Tesla wants to improve driving range with a hybrid li-ion / li-metal battery

In search of improving the battery range of its vehicles, Tesla is conducting its own research. The most recent considers the combined use of lithium-ion and lithium-metal technologies to cover 20% of additional distance.

Led by Jeff Dahn of Dalhousie University, the team of researchers working on batteries for Tesla has developed a range extender system that does not rely on small gasoline engine, but uses lithium-metal.

To increase the range of electric vehicles, seen as the main argument against the massive adoption of this type of energy in transport, researchers are exploring many avenues. Mercedes and IBM are working on a solution based on liquid electrolyte, while others are considering the use of lithium sulfur for a smartphone that works for 5 days. Others, more pragmatic, involve a small gasoline engine serving as a range extender, a solution that even exists for the Model 3 doubling its range.

The idea of ​​Tesla researchers is to merge these two approaches, but keeping them 100% electric. This hybrid battery combines a conventional lithium-ion battery and a lithium-metal battery. If the first has the advantage of longevity, the second is more energy dense at 890 Wh / L against 530 for the Li-ion. However, in its usual form it degrades in just 15 cycles. Fortunately, the team managed to develop a solution guaranteeing 150 cycles before falling below the 80% capacity mark.

Lithium metal used as a reserve for long distances

About 150 battery cycles may seem very low compared to what a lithium battery is capable of, often around 1000 cycles. Tesla has even filed a patent on a 4,000-cycle battery to reach one million miles (1.6 million km). The principle being to use in priority the li-ion part and to keep the reserve of 20% that uses the li-metal part for long distances.

In order to verify that this approach was realistic, the researchers studied the driving habits of owners of electric vehicles. According to them, only 1% of journeys made exceed 325 km. For the majority of them, it would therefore be possible to use hybrid batteries, 99% of the time in lithium-ion and the remaining 1% in lithium-metal without noticing premature wear on the latter.

Contact the author: dominicwood@wheelsjoint.com

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