Tesla Battery Day update flags launch of million mile battery in China first

A news report ahead of Tesla’s much anticipated Battery Day reveals that new electric car battery technology from the company will be released first in China.

The anticipated Tesla Battery Day event is still yet to have a confirmed date, although it is still expected in the month of May according to comments made by CEO and co-founder Elon Musk at the company’s first quarter earnings call for 2020.

A new report from Reuters reveals that Tesla will first launch a “million mile” battery technology – jointly developed with Chinese battery developer Contemporary Amperex Technology Ltd (CATL) – in China, three sources familiar with the matter reportedly told Reuters.

The “million mile” battery was first discussed by Musk at the company’s 2019 “Autonomy Day” in Palo Alto, at which he said: “The new battery pack that is probably going to production next year is designed explicitly for 1 million miles of operation.”

It is significant because according to Musk, Tesla’s Model 3 – which he has slated for a giant “robotaxi” fleet – is designed to last at least that long, and it makes sense then that its battery will also.

For a battery to last a million miles (i.e., 1.6 million kilometres), it needs to be able to cycle (ie discharge and recharge from full to empty and back again) significantly more times than current li-ion battery technology. Current technology typically starts to degrade in low 1,000s of cycles, whereas to be able to last for a million miles, a battery must be able to cycle around 4,000 times.

How Tesla will achieve this is yet to be officially revealed. In September 2019, a team of “academic battery experts” led by Canadian academic and head of Tesla’s battery research team Jeff Dahn, published a paper in the Journal of Electrochemistry stating that the desired lifetime could be achieved using single crystal NMC532/AG cells with optimized electrolytes.

A senior researcher familiar with battery technology told The Driven by email that, “If you look at that paper in greater detail, you can see that they are estimating MUCH higher stability factors for low temperatures.

“The major innovation presented in this paper is one that uses additives, to dramatically improve the cyclability of the electrodes. This makes good sense, because much of the issue with batteries arises from interfacial cyclability.”

Not long after, reports emerged in November that Elon Musk had met with CATL chairman Zeng Yuqun, presumed at the time to be part of the goal to localise parts for the Model 3 being produced at Tesla’s Shanghai Gigafactory 3 (localisation of parts is a major goal for Tesla in China in order to bring manufacturing costs down).

In February, The Driven reported that development of a cobalt-free battery by Tesla and CATL was on the cards, according to another report first made by Reuters.

The use of cobalt in li-ion batteries is highly controversial due to the human rights issues surrounding mining operations in countries such as the Democratic Republic of Congo. It is also expensive, so negating the use of cobalt would kill two birds with one stone: reducing the risk of child miners and making electric cars cheaper.

But this new report from Reuters suggests that lithium-iron-phosphate (LFP) technology might be a part of the picture, not nickel-manganese-cobalt (NMC) as suggested in Dahn’s September paper mentioned above.

More Tesla battery research and patents have come to light in recent weeks, from Tesla’s “tabless” battery patent which reduces the ohmic resistance of a battery by using a conductive edge on the jelly roll instead of connecting the positive and negative terminals of a battery with a tab.

While reducing the resistance in this manner would reduce voltaic loss by the battery and hence increase driving range, which in the long term could improve cyclability, it is not likely it would be by a significant amount but rather be part of a broader approach.

Another paper (currently in pre-print) from Dahn’s research team, reported on by The Driven on Thursday, discusses a hybrid battery approach. This approach, which proposes a way of plating graphite with lithium metal in tandem with a standard lithium-ion cell, could increase driving range of a battery by 20%, the researchers suggest.

Which brings us back to a report from little-known Chinese automotive news site called Krypton 36.

As The Driven reported in February, this news site covered a comment from a Chinese source close to Tesla that, “The new battery independently developed by Tesla is a combination of dry battery technology and supercapacitor. The specific composition is expected to be explained at the Tesla Battery Conference in April.”

This is also important, because according to Musk, speaking at Tesla’s fourth quarter earnings call in 2019, the acquisition of Maxwell Technologies and the ” ultracaps” technology that gave Tesla access to, is an “important piece of the puzzle”.

Combining standard lithium-ion batteries with super capacitors (one specialisation of Maxwell batteries that Tesla acquired in May 2019) could greatly increase range, according to the expert The Driven has been communicating with.

“One thing that is happening is the combination of conventional batteries and supercaps to form so-called hybrid batteries. These tend to have intermediate properties of these two devices. An advantage in the literate of these is that they have dramatically improved device cyclabilities (can be 10,000’s of cycles, unlike LIBs which start to degrade in the 1000’s ranges),” the expert said in a note by email.